| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/10/29 18:09 | flow | patch-triage |
13mArgs:null Results: {
"EnableConfigs": [
"SYSVIPC",
"SYSVIPC_SYSCTL"
],
"FocusSymbols": [
"proc_ipc_sem_dointvec",
"do_semtimedop",
"ksys_semtimedop",
"__do_semtimedop",
"sem_init_ns"
],
"KMSANReasoning": "The patch series serializes writes to the sysctl kernel.sem parameter using a new mutex (sem_ctls_mutex), adds validation checks on sem_ctls values, and adds the GFP_KERNEL_ACCOUNT flag to kvmalloc_objs() in do_semtimedop().\n\nKMSAN is not needed because:\n1. The local stack array `sem_ctls` in `proc_ipc_sem_dointvec()` is fully initialized from `ns-\u003esem_ctls` prior to invoking `proc_dointvec()`.\n2. In `do_semtimedop()`, the allocated `sops` array is immediately and fully populated from user space via `copy_from_user()` over the entire requested size (`nsops * sizeof(*tsops)`) before any elements are accessed.\n3. No uninitialized memory is read, branched upon, or leaked to user space.\n4. Concurrency or locking risks involving the newly added mutex are covered by LOCKDEP, and any out-of-bounds or allocation size issues are covered by KASAN.",
"NeedsKMSAN": false,
"Reasoning": "The patch modifies System V IPC semaphore handling by introducing a mutex to serialize writers to /proc/sys/kernel/sem, validating sem_ctls[2] (semopm) along with semmni, lifting the historical limit on SEMOPM to INT_MAX, and adding GFP_KERNEL_ACCOUNT to kvmalloc_objs in do_semtimedop. These changes modify reachable core IPC syscall handling and sysctl interfaces, warranting fuzzing.",
"WorthFuzzing": true
} |
| 1/1 | 2026/10/29 18:09 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 185a899cb76dd2fbe1ddeb0def8c8c218a00f04f\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Thu Oct 29 18:09:48 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h\nindex 12faca29bbb9c3..c06568ccfca88f 100644\n--- a/include/linux/ipc_namespace.h\n+++ b/include/linux/ipc_namespace.h\n@@ -4,6 +4,7 @@\n \n #include \u003clinux/err.h\u003e\n #include \u003clinux/idr.h\u003e\n+#include \u003clinux/mutex.h\u003e\n #include \u003clinux/rwsem.h\u003e\n #include \u003clinux/notifier.h\u003e\n #include \u003clinux/nsproxy.h\u003e\n@@ -31,6 +32,8 @@ struct ipc_ids {\n struct ipc_namespace {\n \tstruct ipc_ids\tids[3];\n \n+\t/* Serialize kernel.sem writers. */\n+\tstruct mutex\tsem_ctls_mutex;\n \tint\t\tsem_ctls[4];\n \tint\t\tused_sems;\n \ndiff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h\nindex 75aa3b273cd995..d9f961a1592c7b 100644\n--- a/include/uapi/linux/sem.h\n+++ b/include/uapi/linux/sem.h\n@@ -71,16 +71,15 @@ struct seminfo {\n * The values has been chosen to be larger than necessary for any\n * known configuration.\n *\n- * SEMOPM should not be increased beyond 1000, otherwise there is the\n- * risk that semop()/semtimedop() fails due to kernel memory fragmentation when\n- * allocating the sop array.\n+ * SEMOPM is the default maximum number of operations per semop() call. The\n+ * runtime limit can be changed through /proc/sys/kernel/sem.\n */\n \n \n #define SEMMNI 32000 /* \u003c= IPCMNI max # of semaphore identifiers */\n #define SEMMSL 32000 /* \u003c= INT_MAX max num of semaphores per id */\n #define SEMMNS (SEMMNI*SEMMSL) /* \u003c= INT_MAX max # of semaphores in system */\n-#define SEMOPM 500\t /* \u003c= 1 000 max num of ops per semop call */\n+#define SEMOPM 500\t /* \u003c= INT_MAX max num of ops per semop call */\n #define SEMVMX 32767 /* \u003c= 32767 semaphore maximum value */\n #define SEMAEM SEMVMX /* adjust on exit max value */\n \ndiff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c\nindex d038d944257f60..0e3608258fe297 100644\n--- a/ipc/ipc_sysctl.c\n+++ b/ipc/ipc_sysctl.c\n@@ -51,21 +51,38 @@ static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,\n static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\n \tvoid *buffer, size_t *lenp, loff_t *ppos)\n {\n+\tstruct ctl_table ipc_table;\n \tstruct ipc_namespace *ns =\n \t\tcontainer_of(table-\u003edata, struct ipc_namespace, sem_ctls);\n-\tint ret, semmni;\n+\tint sem_ctls[ARRAY_SIZE(ns-\u003esem_ctls)];\n+\tsize_t i;\n+\tint ret;\n+\n+\tif (!write)\n+\t\treturn proc_dointvec(table, write, buffer, lenp, ppos);\n \n-\tsemmni = ns-\u003esem_ctls[3];\n-\tret = proc_dointvec(table, write, buffer, lenp, ppos);\n+\tmutex_lock(\u0026ns-\u003esem_ctls_mutex);\n+\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\n+\t\tsem_ctls[i] = READ_ONCE(ns-\u003esem_ctls[i]);\n \n-\tif (!ret)\n-\t\tret = sem_check_semmni(ns);\n+\tipc_table = *table;\n+\tipc_table.data = sem_ctls;\n \n-\t/*\n-\t * Reset the semmni value if an error happens.\n-\t */\n+\tret = proc_dointvec(\u0026ipc_table, write, buffer, lenp, ppos);\n \tif (ret)\n-\t\tns-\u003esem_ctls[3] = semmni;\n+\t\tgoto out_unlock;\n+\n+\tif (sem_ctls[2] \u003c 0 ||\n+\t sem_ctls[3] \u003c 0 || sem_ctls[3] \u003e ipc_mni) {\n+\t\tret = -ERANGE;\n+\t\tgoto out_unlock;\n+\t}\n+\n+\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\n+\t\tWRITE_ONCE(ns-\u003esem_ctls[i], sem_ctls[i]);\n+\n+out_unlock:\n+\tmutex_unlock(\u0026ns-\u003esem_ctls_mutex);\n \treturn ret;\n }\n \ndiff --git a/ipc/sem.c b/ipc/sem.c\nindex 5ec41de7e85b2b..098e483ae8d3c1 100644\n--- a/ipc/sem.c\n+++ b/ipc/sem.c\n@@ -248,6 +248,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);\n \n void sem_init_ns(struct ipc_namespace *ns)\n {\n+\tmutex_init(\u0026ns-\u003esem_ctls_mutex);\n \tns-\u003esc_semmsl = SEMMSL;\n \tns-\u003esc_semmns = SEMMNS;\n \tns-\u003esc_semopm = SEMOPM;\n@@ -2234,7 +2235,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,\n \t\treturn -EINVAL;\n \n \tif (nsops \u003e SEMOPM_FAST) {\n-\t\tsops = kvmalloc_objs(*sops, nsops);\n+\t\tsops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);\n \t\tif (sops == NULL)\n \t\t\treturn -ENOMEM;\n \t}\ndiff --git a/ipc/util.h b/ipc/util.h\nindex a55d6cebe6d3b0..51b4efa3d6db01 100644\n--- a/ipc/util.h\n+++ b/ipc/util.h\n@@ -245,15 +245,6 @@ int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,\n void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,\n \t\tvoid (*free)(struct ipc_namespace *, struct kern_ipc_perm *));\n \n-static inline int sem_check_semmni(struct ipc_namespace *ns) {\n-\t/*\n-\t * Check semmni range [0, ipc_mni]\n-\t * semmni is the last element of sem_ctls[4] array\n-\t */\n-\treturn ((ns-\u003esem_ctls[3] \u003c 0) || (ns-\u003esem_ctls[3] \u003e ipc_mni))\n-\t\t? -ERANGE : 0;\n-}\n-\n #ifdef CONFIG_COMPAT\n #include \u003clinux/compat.h\u003e\n struct compat_ipc_perm {\n"
} |
| 2/1 | 2026/10/29 18:09 | agent | patch-evaluator |
5mModel:core Args: null Results: {
"EnableConfigs": [
"SYSVIPC",
"SYSVIPC_SYSCTL"
],
"FocusSymbols": [
"proc_ipc_sem_dointvec",
"do_semtimedop",
"ksys_semtimedop",
"__do_semtimedop",
"sem_init_ns"
],
"Reasoning": "The patch modifies System V IPC semaphore handling by introducing a mutex to serialize writers to /proc/sys/kernel/sem, validating sem_ctls[2] (semopm) along with semmni, lifting the historical limit on SEMOPM to INT_MAX, and adding GFP_KERNEL_ACCOUNT to kvmalloc_objs in do_semtimedop. These changes modify reachable core IPC syscall handling and sysctl interfaces, warranting fuzzing.",
"WorthFuzzing": true
}Instruction: You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.
IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.
================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.
- REACHABILITY IS THE PRIMARY GATE:
Fuzzing can only discover bugs in code that can actually execute in standard virtualized
environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
regardless of whether it adds assertions or complex logic.
- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
Patch authors routinely label changes as "cleanups", "refactorings", or state
"No functional change intended". Do NOT take these claims at face value.
Code refactorings that rearrange logic, introduce helper functions, or alter state management
in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
If reachable executable code is modified or refactored, it MUST be fuzzed.
- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
Even if the author believes the invariant always holds, fuzzing is essential to verify whether
an unusual sequence of operations can violate it.
================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:
- Non-kernel and non-executable changes:
* Modifications to Documentation/, comments, or spelling fixes.
* User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
that do not affect the compiled kernel image (vmlinux) or kernel modules.
* Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
that do not alter control flow or data structures.
* Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
* Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
* Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
physical PCI hot-unplug or manual sysfs driver unbinding.
* Code paths exclusive to architectures other than the target architecture.
================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
* Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
* Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
* Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
* Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).
================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:
- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
Do NOT list generic, ubiquitous functions called by almost every program in the corpus
(including, but not limited to: general memory allocators and deallocators, page fault
and trap handlers, or core synchronization primitives; this is not an exhaustive list).
Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
which severely dilutes fuzzing effort away from the actual changes.
- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
List functions that specifically implement the logic being added or altered, or direct API entrypoints
for the subsystem feature under review.
- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).
================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 185a899cb76dd2fbe1ddeb0def8c8c218a00f04f
Author: syz-cluster <triage@syzkaller.com>
Date: Thu Oct 29 18:09:48 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 12faca29bbb9c3..c06568ccfca88f 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -4,6 +4,7 @@
#include <linux/err.h>
#include <linux/idr.h>
+#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/notifier.h>
#include <linux/nsproxy.h>
@@ -31,6 +32,8 @@ struct ipc_ids {
struct ipc_namespace {
struct ipc_ids ids[3];
+ /* Serialize kernel.sem writers. */
+ struct mutex sem_ctls_mutex;
int sem_ctls[4];
int used_sems;
diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index 75aa3b273cd995..d9f961a1592c7b 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -71,16 +71,15 @@ struct seminfo {
* The values has been chosen to be larger than necessary for any
* known configuration.
*
- * SEMOPM should not be increased beyond 1000, otherwise there is the
- * risk that semop()/semtimedop() fails due to kernel memory fragmentation when
- * allocating the sop array.
+ * SEMOPM is the default maximum number of operations per semop() call. The
+ * runtime limit can be changed through /proc/sys/kernel/sem.
*/
#define SEMMNI 32000 /* <= IPCMNI max # of semaphore identifiers */
#define SEMMSL 32000 /* <= INT_MAX max num of semaphores per id */
#define SEMMNS (SEMMNI*SEMMSL) /* <= INT_MAX max # of semaphores in system */
-#define SEMOPM 500 /* <= 1 000 max num of ops per semop call */
+#define SEMOPM 500 /* <= INT_MAX max num of ops per semop call */
#define SEMVMX 32767 /* <= 32767 semaphore maximum value */
#define SEMAEM SEMVMX /* adjust on exit max value */
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index d038d944257f60..0e3608258fe297 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -51,21 +51,38 @@ static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,
static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
+ struct ctl_table ipc_table;
struct ipc_namespace *ns =
container_of(table->data, struct ipc_namespace, sem_ctls);
- int ret, semmni;
+ int sem_ctls[ARRAY_SIZE(ns->sem_ctls)];
+ size_t i;
+ int ret;
+
+ if (!write)
+ return proc_dointvec(table, write, buffer, lenp, ppos);
- semmni = ns->sem_ctls[3];
- ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ mutex_lock(&ns->sem_ctls_mutex);
+ for (i = 0; i < ARRAY_SIZE(sem_ctls); i++)
+ sem_ctls[i] = READ_ONCE(ns->sem_ctls[i]);
- if (!ret)
- ret = sem_check_semmni(ns);
+ ipc_table = *table;
+ ipc_table.data = sem_ctls;
- /*
- * Reset the semmni value if an error happens.
- */
+ ret = proc_dointvec(&ipc_table, write, buffer, lenp, ppos);
if (ret)
- ns->sem_ctls[3] = semmni;
+ goto out_unlock;
+
+ if (sem_ctls[2] < 0 ||
+ sem_ctls[3] < 0 || sem_ctls[3] > ipc_mni) {
+ ret = -ERANGE;
+ goto out_unlock;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(sem_ctls); i++)
+ WRITE_ONCE(ns->sem_ctls[i], sem_ctls[i]);
+
+out_unlock:
+ mutex_unlock(&ns->sem_ctls_mutex);
return ret;
}
diff --git a/ipc/sem.c b/ipc/sem.c
index 5ec41de7e85b2b..098e483ae8d3c1 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -248,6 +248,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
void sem_init_ns(struct ipc_namespace *ns)
{
+ mutex_init(&ns->sem_ctls_mutex);
ns->sc_semmsl = SEMMSL;
ns->sc_semmns = SEMMNS;
ns->sc_semopm = SEMOPM;
@@ -2234,7 +2235,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
return -EINVAL;
if (nsops > SEMOPM_FAST) {
- sops = kvmalloc_objs(*sops, nsops);
+ sops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);
if (sops == NULL)
return -ENOMEM;
}
diff --git a/ipc/util.h b/ipc/util.h
index a55d6cebe6d3b0..51b4efa3d6db01 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -245,15 +245,6 @@ int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
void (*free)(struct ipc_namespace *, struct kern_ipc_perm *));
-static inline int sem_check_semmni(struct ipc_namespace *ns) {
- /*
- * Check semmni range [0, ipc_mni]
- * semmni is the last element of sem_ctls[4] array
- */
- return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > ipc_mni))
- ? -ERANGE : 0;
-}
-
#ifdef CONFIG_COMPAT
#include <linux/compat.h>
struct compat_ipc_perm {
|
| 3/2 | 2026/10/29 18:09 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 4738 output: 34 thoughts: 403 Thoughts: **Analyzing the Semantic Changes** Okay, let's break down this patch. My immediate focus is on understanding the scope of the modifications. It appears we are making some adjustments to semaphore control structures and their management within the IPC namespace. The code touches several key areas, so let's walk through it methodically. First, I see a new mutex, `sem_ctls_mutex`, being introduced into the `ipc_namespace` structure in `include/linux/ipc_namespace.h`. That immediately piques my interest. It strongly suggests a move towards protecting access to the semaphore control parameters, likely to ensure data integrity during concurrent operations. Then, there are some comment changes in `include/uapi/linux/sem.h`. Usually, I wouldn't worry too much about comments, but I'll make a note of the SEMOPM changes because they are in a header. Let's make a mental note to see if there is any meaning here. Next, `ipc_sysctl.c` has been modified, specifically `proc_ipc_sem_dointvec`. It's reading and writing semaphore control values. The important part is that a local copy, `sem_ctls`, is created within a mutex lock, which is then used in a call to `proc_dointvec`. Afterwards, the changed values are written back to `ns->sem_ctls` using `WRITE_ONCE`. This reinforces my initial thought about concurrency protection. The use of `WRITE_ONCE` is a good practice. It's also making some bounds checks in the process: `sem_ctls[2] < 0 || sem_ctls[3] < 0 || sem_ctls[3] > ipc_mni`. In `ipc/sem.c`, I see `sem_init_ns` is initializing the mutex `ns->sem_ctls_mutex`, solidifying the picture. But, here's the more interesting part: `do_semtimedop` changes the allocation flag. It has been changed from `kvmalloc_objs(*sops, nsops);` to `kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);`. I need to figure out what's going on here. I am slightly concerned about the addition of flags like `GFP_KERNEL_ACCOUNT`. Let's clarify its function; is it related to memory accounting or something else? I'll need to check the definition or surrounding code of `kvmalloc_objs` within `ipc/sem.c` to see how this flag is being used. Finally, `ipc/util.h` removes `sem_check_semmni`. I need to understand why this function has been removed. Is its functionality now handled elsewhere, or has it become redundant? I'll need to investigate where `sem_check_semmni` was used previously and see if that logic is now handled in the new code. Okay, let's use `grepper` or `read-file` to check `ipc/sem.c` around line 2234 to figure out the use of `kvmalloc_objs` and how the memory flag affects it. |
| 4/2 | 2026/10/29 18:10 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 2220,
"LineCount": 40
}Results: {
"Contents": "2220:\t\treturn error;\n2221:\t}\n2222:\t\n2223:\tstatic long do_semtimedop(int semid, struct sembuf __user *tsops,\n2224:\t\t\tunsigned int nsops, const struct timespec64 *timeout)\n2225:\t{\n2226:\t\tstruct sembuf fast_sops[SEMOPM_FAST];\n2227:\t\tstruct sembuf *sops = fast_sops;\n2228:\t\tstruct ipc_namespace *ns;\n2229:\t\tint ret;\n2230:\t\n2231:\t\tns = current-\u003ensproxy-\u003eipc_ns;\n2232:\t\tif (nsops \u003e ns-\u003esc_semopm)\n2233:\t\t\treturn -E2BIG;\n2234:\t\tif (nsops \u003c 1)\n2235:\t\t\treturn -EINVAL;\n2236:\t\n2237:\t\tif (nsops \u003e SEMOPM_FAST) {\n2238:\t\t\tsops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);\n2239:\t\t\tif (sops == NULL)\n2240:\t\t\t\treturn -ENOMEM;\n2241:\t\t}\n2242:\t\n2243:\t\tif (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {\n2244:\t\t\tret = -EFAULT;\n2245:\t\t\tgoto out_free;\n2246:\t\t}\n2247:\t\n2248:\t\tret = __do_semtimedop(semid, sops, nsops, timeout, ns);\n2249:\t\n2250:\tout_free:\n2251:\t\tif (sops != fast_sops)\n2252:\t\t\tkvfree(sops);\n2253:\t\n2254:\t\treturn ret;\n2255:\t}\n2256:\t\n2257:\tlong ksys_semtimedop(int semid, struct sembuf __user *tsops,\n2258:\t\t\t unsigned int nsops, const struct __kernel_timespec __user *timeout)\n2259:\t{\n"
} |
| 5/2 | 2026/10/29 18:10 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 6437 output: 35 thoughts: 14 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into `ipc/ipc_sysctl.c`** Alright, time to get to it. Let's start with `ipc/ipc_sysctl.c`. The `sysctl` interface for IPC is notoriously tricky, and this is where it's likely handled. I need to refresh my memory on the interactions here, especially around the exposed parameters and their relationships. I'm immediately thinking about potential race conditions and atomicity issues, particularly when dealing with shared memory segments or message queues. It's also likely this code is where the kernel's resource limits for IPC objects are configured. I'm going to want to see how these values are validated and enforced. It's possible I'll also find some interesting hooks for tracing or auditing IPC usage in here. So, let's get into the details of the implementation. I'll focus on anything related to security implications, performance and resource consumption. Let's see what gems are buried in the source code. |
| 6/2 | 2026/10/29 18:10 | tool | read-file |
0mArgs:{
"File": "ipc/ipc_sysctl.c",
"FirstLine": 40,
"LineCount": 55
}Results: {
"Contents": " 40:\t\tint dummy = 0;\n 41:\t\n 42:\t\tmemcpy(\u0026ipc_table, table, sizeof(ipc_table));\n 43:\t\tipc_table.data = \u0026dummy;\n 44:\t\n 45:\t\tif (write)\n 46:\t\t\tpr_info_once(\"writing to auto_msgmni has no effect\");\n 47:\t\n 48:\t\treturn proc_dointvec_minmax(\u0026ipc_table, write, buffer, lenp, ppos);\n 49:\t}\n 50:\t\n 51:\tstatic int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\n 52:\t\tvoid *buffer, size_t *lenp, loff_t *ppos)\n 53:\t{\n 54:\t\tstruct ctl_table ipc_table;\n 55:\t\tstruct ipc_namespace *ns =\n 56:\t\t\tcontainer_of(table-\u003edata, struct ipc_namespace, sem_ctls);\n 57:\t\tint sem_ctls[ARRAY_SIZE(ns-\u003esem_ctls)];\n 58:\t\tsize_t i;\n 59:\t\tint ret;\n 60:\t\n 61:\t\tif (!write)\n 62:\t\t\treturn proc_dointvec(table, write, buffer, lenp, ppos);\n 63:\t\n 64:\t\tmutex_lock(\u0026ns-\u003esem_ctls_mutex);\n 65:\t\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\n 66:\t\t\tsem_ctls[i] = READ_ONCE(ns-\u003esem_ctls[i]);\n 67:\t\n 68:\t\tipc_table = *table;\n 69:\t\tipc_table.data = sem_ctls;\n 70:\t\n 71:\t\tret = proc_dointvec(\u0026ipc_table, write, buffer, lenp, ppos);\n 72:\t\tif (ret)\n 73:\t\t\tgoto out_unlock;\n 74:\t\n 75:\t\tif (sem_ctls[2] \u003c 0 ||\n 76:\t\t sem_ctls[3] \u003c 0 || sem_ctls[3] \u003e ipc_mni) {\n 77:\t\t\tret = -ERANGE;\n 78:\t\t\tgoto out_unlock;\n 79:\t\t}\n 80:\t\n 81:\t\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\n 82:\t\t\tWRITE_ONCE(ns-\u003esem_ctls[i], sem_ctls[i]);\n 83:\t\n 84:\tout_unlock:\n 85:\t\tmutex_unlock(\u0026ns-\u003esem_ctls_mutex);\n 86:\t\treturn ret;\n 87:\t}\n 88:\t\n 89:\tint ipc_mni = IPCMNI;\n 90:\tint ipc_mni_shift = IPCMNI_SHIFT;\n 91:\tint ipc_min_cycle = RADIX_TREE_MAP_SIZE;\n 92:\t\n 93:\tstatic const struct ctl_table ipc_sysctls[] = {\n 94:\t\t{\n"
} |
| 7/2 | 2026/10/29 18:10 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7528 output: 43 thoughts: 58 Thoughts: Okay, here's my thought process on this, distilled down to a first-person summary, keeping in mind my field of expertise: **Diving into Semaphore Control Structure Mapping** Right, so I need to get a clear picture of how those `sem_ctls` are actually organized in memory and, crucially, what each index within that structure represents. My first instinct, given my experience, is to zero in on the core of the kernel's semaphore implementation. I'll need to locate the definition or mapping. Therefore, my immediate plan is to conduct a search. I'll start with the most likely locations, focusing on `ipc/sem.c` which, naturally, would hold the core semaphore functions. I'll also check `include/linux/ipc_namespace.h` since this is where the core IPC namespaces would most likely be defined. I'll use keywords `sem_ctls` and `sc_sem` (which I suspect is a shorter version), to catch variations in naming. This should quickly lead me to the relevant data structures and indexing logic. |
| 8/2 | 2026/10/29 18:10 | tool | grepper |
0mArgs:{
"Expression": "sc_sem|sem_ctls",
"PathPrefixes": [
"include/linux/ipc_namespace.h",
"ipc/"
]
}Results: {
"Output": "include/linux/ipc_namespace.h=32=struct ipc_namespace {\n--\ninclude/linux/ipc_namespace.h-35-\t/* Serialize kernel.sem writers. */\ninclude/linux/ipc_namespace.h:36:\tstruct mutex\tsem_ctls_mutex;\ninclude/linux/ipc_namespace.h:37:\tint\t\tsem_ctls[4];\ninclude/linux/ipc_namespace.h-38-\tint\t\tused_sems;\n--\nipc/ipc_sysctl.c=51=static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\n--\nipc/ipc_sysctl.c-55-\tstruct ipc_namespace *ns =\nipc/ipc_sysctl.c:56:\t\tcontainer_of(table-\u003edata, struct ipc_namespace, sem_ctls);\nipc/ipc_sysctl.c:57:\tint sem_ctls[ARRAY_SIZE(ns-\u003esem_ctls)];\nipc/ipc_sysctl.c-58-\tsize_t i;\n--\nipc/ipc_sysctl.c-63-\nipc/ipc_sysctl.c:64:\tmutex_lock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c:65:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:66:\t\tsem_ctls[i] = READ_ONCE(ns-\u003esem_ctls[i]);\nipc/ipc_sysctl.c-67-\nipc/ipc_sysctl.c-68-\tipc_table = *table;\nipc/ipc_sysctl.c:69:\tipc_table.data = sem_ctls;\nipc/ipc_sysctl.c-70-\n--\nipc/ipc_sysctl.c-74-\nipc/ipc_sysctl.c:75:\tif (sem_ctls[2] \u003c 0 ||\nipc/ipc_sysctl.c:76:\t sem_ctls[3] \u003c 0 || sem_ctls[3] \u003e ipc_mni) {\nipc/ipc_sysctl.c-77-\t\tret = -ERANGE;\n--\nipc/ipc_sysctl.c-80-\nipc/ipc_sysctl.c:81:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:82:\t\tWRITE_ONCE(ns-\u003esem_ctls[i], sem_ctls[i]);\nipc/ipc_sysctl.c-83-\nipc/ipc_sysctl.c-84-out_unlock:\nipc/ipc_sysctl.c:85:\tmutex_unlock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c-86-\treturn ret;\n--\nipc/ipc_sysctl.c=93=static const struct ctl_table ipc_sysctls[] = {\n--\nipc/ipc_sysctl.c-163-\t\t.procname\t= \"sem\",\nipc/ipc_sysctl.c:164:\t\t.data\t\t= \u0026init_ipc_ns.sem_ctls,\nipc/ipc_sysctl.c-165-\t\t.maxlen\t\t= 4*sizeof(int),\n--\nipc/ipc_sysctl.c=262=bool setup_ipc_sysctls(struct ipc_namespace *ns)\n--\nipc/ipc_sysctl.c-293-\nipc/ipc_sysctl.c:294:\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.sem_ctls)\nipc/ipc_sysctl.c:295:\t\t\t\ttbl[i].data = \u0026ns-\u003esem_ctls;\nipc/ipc_sysctl.c-296-#ifdef CONFIG_CHECKPOINT_RESTORE\n--\nipc/sem.c=174=static int sysvipc_sem_proc_show(struct seq_file *s, void *it);\n--\nipc/sem.c-243-\nipc/sem.c:244:#define sc_semmsl\tsem_ctls[0]\nipc/sem.c:245:#define sc_semmns\tsem_ctls[1]\nipc/sem.c:246:#define sc_semopm\tsem_ctls[2]\nipc/sem.c:247:#define sc_semmni\tsem_ctls[3]\nipc/sem.c-248-\nipc/sem.c=249=void sem_init_ns(struct ipc_namespace *ns)\nipc/sem.c-250-{\nipc/sem.c:251:\tmutex_init(\u0026ns-\u003esem_ctls_mutex);\nipc/sem.c:252:\tns-\u003esc_semmsl = SEMMSL;\nipc/sem.c:253:\tns-\u003esc_semmns = SEMMNS;\nipc/sem.c:254:\tns-\u003esc_semopm = SEMOPM;\nipc/sem.c:255:\tns-\u003esc_semmni = SEMMNI;\nipc/sem.c-256-\tns-\u003eused_sems = 0;\n--\nipc/sem.c=532=static int newary(struct ipc_namespace *ns, struct ipc_params *params)\n--\nipc/sem.c-542-\t\treturn -EINVAL;\nipc/sem.c:543:\tif (ns-\u003eused_sems + nsems \u003e ns-\u003esc_semmns)\nipc/sem.c-544-\t\treturn -ENOSPC;\n--\nipc/sem.c-574-\t/* ipc_addid() locks sma upon success. */\nipc/sem.c:575:\tretval = ipc_addid(\u0026sem_ids(ns), \u0026sma-\u003esem_perm, ns-\u003esc_semmni);\nipc/sem.c-576-\tif (retval \u003c 0) {\n--\nipc/sem.c=603=long ksys_semget(key_t key, int nsems, int semflg)\n--\nipc/sem.c-614-\nipc/sem.c:615:\tif (nsems \u003c 0 || nsems \u003e ns-\u003esc_semmsl)\nipc/sem.c-616-\t\treturn -EINVAL;\n--\nipc/sem.c=1309=static int semctl_info(struct ipc_namespace *ns, int semid,\n--\nipc/sem.c-1320-\tmemset(\u0026seminfo, 0, sizeof(seminfo));\nipc/sem.c:1321:\tseminfo.semmni = ns-\u003esc_semmni;\nipc/sem.c:1322:\tseminfo.semmns = ns-\u003esc_semmns;\nipc/sem.c:1323:\tseminfo.semmsl = ns-\u003esc_semmsl;\nipc/sem.c:1324:\tseminfo.semopm = ns-\u003esc_semopm;\nipc/sem.c-1325-\tseminfo.semvmx = SEMVMX;\n--\nipc/sem.c=1984=long __do_semtimedop(int semid, struct sembuf *sops,\n--\nipc/sem.c-2000-\t\treturn -EINVAL;\nipc/sem.c:2001:\tif (nsops \u003e ns-\u003esc_semopm)\nipc/sem.c-2002-\t\treturn -E2BIG;\n--\nipc/sem.c=2223=static long do_semtimedop(int semid, struct sembuf __user *tsops,\n--\nipc/sem.c-2231-\tns = current-\u003ensproxy-\u003eipc_ns;\nipc/sem.c:2232:\tif (nsops \u003e ns-\u003esc_semopm)\nipc/sem.c-2233-\t\treturn -E2BIG;\n"
} |
| 9/2 | 2026/10/29 18:10 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 9844 output: 20 thoughts: 592 Thoughts: **Analyzing this Commit: A Deep Dive into Semaphore Control**
Okay, let's break down this commit. The core is about refining semaphore control within the kernel, specifically addressing how limits are set and enforced. First, the commit log would be ideal, but without it, the diff itself provides the context.
My initial impression is that this is a good change, hardening the semaphore subsystem.
Here's the breakdown:
1. We see a new mutex, `sem_ctls_mutex`, added to the `ipc_namespace` struct in `include/linux/ipc_namespace.h`. This immediately flags the commit's intent: concurrency control. Looks like this new mutex is introduced to protect the semaphore control values.
2. Next, in `include/uapi/linux/sem.h`, the definition of `SEMOPM` gets some clarification. The comment about not increasing it beyond 1000 is now replaced. It now describes SEMOPM as the *default* maximum operations per `semop()` call, with runtime adjustment via `/proc/sys/kernel/sem`. And it's set to 500 now. This is a subtle but significant change; shifting the constraint from a hard-coded limit to a default, configurable via the sysctl.
3. The meat of the change is in `ipc/ipc_sysctl.c`. The `proc_ipc_sem_dointvec` function, responsible for handling writes to the semaphore control parameters through `/proc`, is significantly revised. Previously, it directly modified the `ns->sem_ctls` array. The code is now using a mutex `ns->sem_ctls_mutex`, a copy of the semaphore control values, modifies the copy, validates the modified values, and then atomically updates the `ns->sem_ctls` array using `WRITE_ONCE`. This introduces a crucial layer of protection against race conditions.
A significant change here is that not only `semmni` (maximum number of semaphore identifiers) is checked, but also `semopm` (maximum number of operations per semop call) is validated to be non-negative and not greater than `ipc_mni`. This is important because it ensures that changes to `semopm` will not have unexpected behaviour.
4. Finally, `ipc/sem.c` gets updated. `sem_init_ns` now initializes the newly added `sem_ctls_mutex`. The `do_semtimedop` function's handling of `nsops > SEMOPM_FAST` has changed. The crucial detail is the use of `GFP_KERNEL_ACCOUNT` in `kvmalloc_objs`, which suggests memory accounting is now being performed. I need to refresh myself about that `kvmalloc_objs` definition, as it could be relevant to the safety improvements.
In summary, this commit is about improving the concurrency safety and flexibility of semaphore control within the kernel, with particular emphasis on memory management in the semaphore operations. The added mutex, the new checks, and the use of memory accounting are all excellent signs of a well-considered improvement. This is good, safe work.
|
| 10/2 | 2026/10/29 18:10 | tool | grepper |
0mArgs:{
"Expression": "#define kvmalloc_objs"
}Results: {
"Output": "include/linux/slab.h=1073=void *kmalloc_nolock(size_t size, gfp_t gfp_flags, int node);\n--\ninclude/linux/slab.h-1164-\t__alloc_objs(kvmalloc, default_gfp(__VA_ARGS__), typeof(P), 1)\ninclude/linux/slab.h:1165:#define kvmalloc_objs(P, COUNT, ...) \\\ninclude/linux/slab.h-1166-\t__alloc_objs(kvmalloc, default_gfp(__VA_ARGS__), typeof(P), COUNT)\n"
} |
| 11/2 | 2026/10/29 18:10 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11280 output: 34 thoughts: 344 Thoughts: **My Analysis of the Semantics of Semaphore Operations**
Okay, so I'm looking at this `kvmalloc_objs` function and I see it's taking flags through `__VA_ARGS__`, which defaults to `GFP_KERNEL` if nothing is specified via `default_gfp(__VA_ARGS__)`. Aha! Now it's being called with `GFP_KERNEL_ACCOUNT`. That's interesting, meaning that the memory allocated for `sops` is now being accounted for in the memcg. I wonder why this change was necessary...
Oh, right! The `SEMOPM` limit used to cap the number of semaphore operations, but now it can be set much higher via `/proc/sys/kernel/sem`, potentially up to `INT_MAX`. This means that userspace, when using a large `nsops`, could trigger a massive memory allocation within `do_semtimedop`.
Let me re-examine `do_semtimedop`. Yep, there it is:
```c
if (nsops > ns->sc_semopm)
return -E2BIG;
if (nsops < 1)
return -EINVAL;
if (nsops > SEMOPM_FAST) {
sops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);
if (sops == NULL)
return -ENOMEM;
}
if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
...
ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
```
Okay, so if `nsops` is large and exceeds `SEMOPM_FAST`, we allocate `sops` with `kvmalloc_objs`. But what happens within `__do_semtimedop` if `nsops` is *really* large? I need to check the implementation of `__do_semtimedop` in `ipc/sem.c` to see how the code handles a potentially huge `nsops` value. Gotta keep digging!
|
| 12/2 | 2026/10/29 18:11 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 1980,
"LineCount": 80
}Results: {
"Contents": "1980:\tout:\n1981:\t\treturn un;\n1982:\t}\n1983:\t\n1984:\tlong __do_semtimedop(int semid, struct sembuf *sops,\n1985:\t\t\tunsigned int nsops, const struct timespec64 *timeout,\n1986:\t\t\tstruct ipc_namespace *ns)\n1987:\t{\n1988:\t\tint error = -EINVAL;\n1989:\t\tstruct sem_array *sma;\n1990:\t\tstruct sembuf *sop;\n1991:\t\tstruct sem_undo *un;\n1992:\t\tint max, locknum;\n1993:\t\tbool undos = false, alter = false, dupsop = false;\n1994:\t\tstruct sem_queue queue;\n1995:\t\tunsigned long dup = 0;\n1996:\t\tktime_t expires, *exp = NULL;\n1997:\t\tbool timed_out = false;\n1998:\t\n1999:\t\tif (nsops \u003c 1 || semid \u003c 0)\n2000:\t\t\treturn -EINVAL;\n2001:\t\tif (nsops \u003e ns-\u003esc_semopm)\n2002:\t\t\treturn -E2BIG;\n2003:\t\n2004:\t\tif (timeout) {\n2005:\t\t\tif (!timespec64_valid(timeout))\n2006:\t\t\t\treturn -EINVAL;\n2007:\t\t\texpires = ktime_add_safe(ktime_get(),\n2008:\t\t\t\t\ttimespec64_to_ktime(*timeout));\n2009:\t\t\texp = \u0026expires;\n2010:\t\t}\n2011:\t\n2012:\t\n2013:\t\tmax = 0;\n2014:\t\tfor (sop = sops; sop \u003c sops + nsops; sop++) {\n2015:\t\t\tunsigned long mask = 1ULL \u003c\u003c ((sop-\u003esem_num) % BITS_PER_LONG);\n2016:\t\n2017:\t\t\tif (sop-\u003esem_num \u003e= max)\n2018:\t\t\t\tmax = sop-\u003esem_num;\n2019:\t\t\tif (sop-\u003esem_flg \u0026 SEM_UNDO)\n2020:\t\t\t\tundos = true;\n2021:\t\t\tif (dup \u0026 mask) {\n2022:\t\t\t\t/*\n2023:\t\t\t\t * There was a previous alter access that appears\n2024:\t\t\t\t * to have accessed the same semaphore, thus use\n2025:\t\t\t\t * the dupsop logic. \"appears\", because the detection\n2026:\t\t\t\t * can only check % BITS_PER_LONG.\n2027:\t\t\t\t */\n2028:\t\t\t\tdupsop = true;\n2029:\t\t\t}\n2030:\t\t\tif (sop-\u003esem_op != 0) {\n2031:\t\t\t\talter = true;\n2032:\t\t\t\tdup |= mask;\n2033:\t\t\t}\n2034:\t\t}\n2035:\t\n2036:\t\tif (undos) {\n2037:\t\t\t/* On success, find_alloc_undo takes the rcu_read_lock */\n2038:\t\t\tun = find_alloc_undo(ns, semid);\n2039:\t\t\tif (IS_ERR(un)) {\n2040:\t\t\t\terror = PTR_ERR(un);\n2041:\t\t\t\tgoto out;\n2042:\t\t\t}\n2043:\t\t} else {\n2044:\t\t\tun = NULL;\n2045:\t\t\trcu_read_lock();\n2046:\t\t}\n2047:\t\n2048:\t\tsma = sem_obtain_object_check(ns, semid);\n2049:\t\tif (IS_ERR(sma)) {\n2050:\t\t\trcu_read_unlock();\n2051:\t\t\terror = PTR_ERR(sma);\n2052:\t\t\tgoto out;\n2053:\t\t}\n2054:\t\n2055:\t\terror = -EFBIG;\n2056:\t\tif (max \u003e= sma-\u003esem_nsems) {\n2057:\t\t\trcu_read_unlock();\n2058:\t\t\tgoto out;\n2059:\t\t}\n"
} |
| 13/2 | 2026/10/29 18:11 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 13219 output: 34 thoughts: 16 Thoughts: Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person: **Diving into `__do_semtimedop`** Alright, let's get down to brass tacks. I'm focusing on the next steps within the `__do_semtimedop` function. Given my understanding of kernel internals, I'm immediately thinking about how this function interfaces with the semaphore data structures, and the potential complexities it handles. What are the specific lock acquisition strategies employed? Are we dealing with spinlocks, mutexes, or something more nuanced given the 'timed' aspect of the operation? I'm mentally stepping through the likely control flow. Are we checking for immediate availability of the resources? What's the timeout mechanism—how is it implemented, and how efficiently does it interact with the scheduler? I'm anticipating potential interrupt handling within this function; how gracefully does it deal with preemption scenarios while manipulating semaphore state? Are there any obvious race conditions that could arise during this critical section? I'm also considering the potential for error conditions. What checks are in place for invalid semaphore IDs, out-of-range arguments, or signal interruptions? How granular are the error codes returned, and how easily can they be traced back to the root cause? Are there any potential deadlocks I should be looking out for given the nature of the operations? I know how tricky that can be with semaphores. Finally, I'm mentally parsing the likely path for successful operation. What's the cleanup strategy? Is it robust enough to handle all exceptional conditions? In essence, I want to confirm that there are no "gotchas" in the logic. |
| 14/2 | 2026/10/29 18:11 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 2060,
"LineCount": 70
}Results: {
"Contents": "2060:\t\n2061:\t\terror = -EACCES;\n2062:\t\tif (ipcperms(ns, \u0026sma-\u003esem_perm, alter ? S_IWUGO : S_IRUGO)) {\n2063:\t\t\trcu_read_unlock();\n2064:\t\t\tgoto out;\n2065:\t\t}\n2066:\t\n2067:\t\terror = security_sem_semop(\u0026sma-\u003esem_perm, sops, nsops, alter);\n2068:\t\tif (error) {\n2069:\t\t\trcu_read_unlock();\n2070:\t\t\tgoto out;\n2071:\t\t}\n2072:\t\n2073:\t\terror = -EIDRM;\n2074:\t\tlocknum = sem_lock(sma, sops, nsops);\n2075:\t\t/*\n2076:\t\t * We eventually might perform the following check in a lockless\n2077:\t\t * fashion, considering ipc_valid_object() locking constraints.\n2078:\t\t * If nsops == 1 and there is no contention for sem_perm.lock, then\n2079:\t\t * only a per-semaphore lock is held and it's OK to proceed with the\n2080:\t\t * check below. More details on the fine grained locking scheme\n2081:\t\t * entangled here and why it's RMID race safe on comments at sem_lock()\n2082:\t\t */\n2083:\t\tif (!ipc_valid_object(\u0026sma-\u003esem_perm))\n2084:\t\t\tgoto out_unlock;\n2085:\t\t/*\n2086:\t\t * semid identifiers are not unique - find_alloc_undo may have\n2087:\t\t * allocated an undo structure, it was invalidated by an RMID\n2088:\t\t * and now a new array with received the same id. Check and fail.\n2089:\t\t * This case can be detected checking un-\u003esemid. The existence of\n2090:\t\t * \"un\" itself is guaranteed by rcu.\n2091:\t\t */\n2092:\t\tif (un \u0026\u0026 un-\u003esemid == -1)\n2093:\t\t\tgoto out_unlock;\n2094:\t\n2095:\t\tqueue.sops = sops;\n2096:\t\tqueue.nsops = nsops;\n2097:\t\tqueue.undo = un;\n2098:\t\tqueue.pid = task_tgid(current);\n2099:\t\tqueue.alter = alter;\n2100:\t\tqueue.dupsop = dupsop;\n2101:\t\n2102:\t\terror = perform_atomic_semop(sma, \u0026queue);\n2103:\t\tif (error == 0) { /* non-blocking successful path */\n2104:\t\t\tDEFINE_WAKE_Q(wake_q);\n2105:\t\n2106:\t\t\t/*\n2107:\t\t\t * If the operation was successful, then do\n2108:\t\t\t * the required updates.\n2109:\t\t\t */\n2110:\t\t\tif (alter)\n2111:\t\t\t\tdo_smart_update(sma, sops, nsops, 1, \u0026wake_q);\n2112:\t\t\telse\n2113:\t\t\t\tset_semotime(sma, sops);\n2114:\t\n2115:\t\t\tsem_unlock(sma, locknum);\n2116:\t\t\trcu_read_unlock();\n2117:\t\t\twake_up_q(\u0026wake_q);\n2118:\t\n2119:\t\t\tgoto out;\n2120:\t\t}\n2121:\t\tif (error \u003c 0) /* non-blocking error path */\n2122:\t\t\tgoto out_unlock;\n2123:\t\n2124:\t\t/*\n2125:\t\t * We need to sleep on this operation, so we put the current\n2126:\t\t * task into the pending queue and go to sleep.\n2127:\t\t */\n2128:\t\tif (nsops == 1) {\n2129:\t\t\tstruct sem *curr;\n"
} |
| 15/2 | 2026/10/29 18:11 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 14673 output: 18 thoughts: 176 Thoughts: **Analyzing a Potential Integer Overflow Vulnerability in `do_semtimedop`** Okay, let's dive into this. I'm taking a look at a potential issue related to the handling of a large `nsops` value. My initial thought is to see what happens when `nsops` gets really big. Hold on, right, `sops` is a `struct sembuf *sops`, which is crucial here. Let's see... looking at the `do_semtimedop` function. The critical line is: `if (copy_from_user(sops, tsops, nsops * sizeof(*tsops)))` Aha! `nsops` is an `unsigned int`, which is a key observation. And `sizeof(*tsops)` is, of course, the size of a `struct sembuf`. Now, here's where my alarm bells start ringing. What if that multiplication, `nsops * sizeof(*tsops)`, overflows? That would lead to a much smaller value than intended being passed to `copy_from_user`, potentially leading to a buffer overflow on the kernel side. To properly assess the risk, I need to know the size of `struct sembuf`. It's defined as `unsigned short sem_num`, `short sem_op`, and `short sem_flg`. That's 6 bytes total, right? Hold on a second, let me double-check the exact definition and alignment of `struct sembuf` to be absolutely certain. We can't let any assumptions sneak in. |
| 16/2 | 2026/10/29 18:11 | tool | grepper |
0mArgs:{
"Expression": "struct sembuf \\{"
}Results: {
"Output": "include/uapi/linux/sem.h=25=struct semid_ds {\n--\ninclude/uapi/linux/sem.h-39-/* semop system calls takes an array of these. */\ninclude/uapi/linux/sem.h:40:struct sembuf {\ninclude/uapi/linux/sem.h-41-\tunsigned short sem_num;\t/* semaphore index in array */\n"
} |
| 17/2 | 2026/10/29 18:11 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15307 output: 37 thoughts: 16 Thoughts: Okay, let's dive into this. Here's my take on those initial thoughts: **Peering into the Kernel's Semaphore Landscape** Alright, time to get my hands dirty with `include/uapi/linux/sem.h`. I'm guessing this file is the user-space interface for interacting with the Linux kernel's semaphore mechanisms. I need to refresh my memory on the system call interface. I'm especially interested in how the core structures are defined. What data structures are exposed to userspace? What's the naming convention? Are there any obvious differences or quirks compared to other OS implementations I'm familiar with? I'm anticipating finding definitions for the `sembuf` struct, likely the main tool to make changes to sets of semaphores. I also expect constants for semaphore operations. I should note the size of the datatypes and structure members. Any flags to be mindful of? Let's get to the nitty-gritty and see what treasures this header file holds. |
| 18/2 | 2026/10/29 18:12 | tool | read-file |
0mArgs:{
"File": "include/uapi/linux/sem.h",
"FirstLine": 38,
"LineCount": 20
}Results: {
"Contents": " 38:\t\n 39:\t/* semop system calls takes an array of these. */\n 40:\tstruct sembuf {\n 41:\t\tunsigned short sem_num;\t/* semaphore index in array */\n 42:\t\tshort\t\tsem_op;\t\t/* semaphore operation */\n 43:\t\tshort\t\tsem_flg;\t/* operation flags */\n 44:\t};\n 45:\t\n 46:\t/* arg for semctl system calls. */\n 47:\tunion semun {\n 48:\t\tint val;\t\t\t/* value for SETVAL */\n 49:\t\tstruct semid_ds __user *buf;\t/* buffer for IPC_STAT \u0026 IPC_SET */\n 50:\t\tunsigned short __user *array;\t/* array for GETALL \u0026 SETALL */\n 51:\t\tstruct seminfo __user *__buf;\t/* buffer for IPC_INFO */\n 52:\t\tvoid __user *__pad;\n 53:\t};\n 54:\t\n 55:\tstruct seminfo {\n 56:\t\tint semmap;\n 57:\t\tint semmni;\n"
} |
| 19/2 | 2026/10/29 18:12 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15860 output: 20 thoughts: 188 Thoughts: **Analyzing Potential Integer Overflow in Semaphore Operations** Okay, so I'm digging into this semaphore code, and the first thing that jumps out is the size of `struct sembuf`, it's just 6 bytes, right? Wait a minute, I have to remember that `nsops`, the number of semaphore operations, is an `unsigned int`. Now, I'm thinking, what if someone sets `ns->sc_semopm` to `INT_MAX`, and then, just to push things to the limit, what if `nsops` is `(1U << 30)`? That means `nsops * sizeof(*tsops)` becomes `(1 << 30) * 6`, which I'm pretty sure overflows a 32-bit `size_t` if we were on a 32-bit architecture. Good thing we're on amd64 where `size_t` is 64-bit, but the overflow could hit in `copy_from_user` or `kvmalloc_objs`, I can't quite remember. Hold on, I see it now, it's actually in `kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT)`! Specifically, in the call to `__alloc_objs(kvmalloc, ...)` - I need to figure out what's going on in there! Let me check what `__alloc_objs` does... |
| 20/2 | 2026/10/29 18:12 | tool | grepper |
0mArgs:{
"Expression": "#define __alloc_objs"
}Results: {
"Output": "include/linux/slab.h=1073=void *kmalloc_nolock(size_t size, gfp_t gfp_flags, int node);\n--\ninclude/linux/slab.h-1086- */\ninclude/linux/slab.h:1087:#define __alloc_objs(KMALLOC, GFP, TYPE, COUNT)\t\t\t\t\\\ninclude/linux/slab.h-1088-({\t\t\t\t\t\t\t\t\t\\\n--\ntools/include/linux/slab.h=200=static inline unsigned int kmem_cache_sheaf_size(struct slab_sheaf *sheaf)\n--\ntools/include/linux/slab.h-204-\ntools/include/linux/slab.h:205:#define __alloc_objs(KMALLOC, GFP, TYPE, COUNT)\t\t\t\t\\\ntools/include/linux/slab.h-206-({\t\t\t\t\t\t\t\t\t\\\n"
} |
| 21/2 | 2026/10/29 18:12 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 16599 output: 36 thoughts: 21 Thoughts: Here's a summary of my thought process, as requested: **Diving into Linux Slab Allocation - A Deep Dive** Okay, time to get my hands dirty. I need to understand this specific allocation behavior better. My initial thought is to zero in on the core of the slab allocator. Specifically, I want to examine the code around the `include/linux/slab.h` file, and I’m going to start around line 1087. I anticipate that this section should shed some light on the aspects I'm trying to figure out. I'm hoping to understand a particular slab's internals at this point, so this should prove to be the right place to begin. |
| 22/2 | 2026/10/29 18:12 | tool | read-file |
0mArgs:{
"File": "include/linux/slab.h",
"FirstLine": 1085,
"LineCount": 20
}Results: {
"Contents": "1085:\t * allocated @TYPE objects, or NULL on failure.\n1086:\t */\n1087:\t#define __alloc_objs(KMALLOC, GFP, TYPE, COUNT)\t\t\t\t\\\n1088:\t({\t\t\t\t\t\t\t\t\t\\\n1089:\t\tconst size_t __obj_size = size_mul(sizeof(TYPE), COUNT);\t\\\n1090:\t\t(TYPE *)KMALLOC(__obj_size, GFP);\t\t\t\t\\\n1091:\t})\n1092:\t\n1093:\t/**\n1094:\t * __alloc_flex - Allocate an object that has a trailing flexible array\n1095:\t * @KMALLOC: kmalloc wrapper function to use for allocation.\n1096:\t * @GFP: GFP flags for the allocation.\n1097:\t * @TYPE: type of structure to allocate space for.\n1098:\t * @FAM: The name of the flexible array member of @TYPE structure.\n1099:\t * @COUNT: how many @FAM elements to allocate space for.\n1100:\t *\n1101:\t * Returns: Newly allocated pointer to @TYPE with @COUNT-many trailing\n1102:\t * @FAM elements, or NULL on failure or if @COUNT cannot be represented\n1103:\t * by the member of @TYPE that counts the @FAM elements (annotated via\n1104:\t * __counted_by()).\n"
} |
| 23/2 | 2026/10/29 18:12 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 17161 output: 32 thoughts: 579 Thoughts: **My Analysis of the Potential Vulnerability** Okay, so `size_mul` checks for overflow, and if it happens, it'll return `SIZE_MAX`, which will cause `kmalloc` or `kvmalloc` to fail. But... hold on a minute, what about how the `sysctl` handling itself works? Let's dive into that. I'm looking at `proc_ipc_sem_dointvec` in `ipc/ipc_sysctl.c`. It seems to be the function that handles the `/proc/sys/kernel/sem` writes. The code copies values into a local array, `sem_ctls`, does the write check. It then has a range check. So, the question is, *can* this function be reached? Yes, it's used when we write to the `/proc/sys/kernel/sem` file. This means there *is* a path to control the size via a sysctl! Now the critical questions. Can an unprivileged user, or a container, write to `/proc/sys/kernel/sem`, or root within a user namespace with a new IPC namespace? We need to figure out the permissions. I need to understand who owns this file and what privileges are required to modify it. Back to the code! Let's examine `ipc/ipc_sysctl.c` again. |
| 24/2 | 2026/10/29 18:13 | tool | grepper |
0mArgs:{
"Expression": "proc_ipc_sem_dointvec",
"PathPrefixes": [
"ipc/"
]
}Results: {
"Output": "ipc/ipc_sysctl.c=36=static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,\n--\nipc/ipc_sysctl.c-50-\nipc/ipc_sysctl.c:51:static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\nipc/ipc_sysctl.c-52-\tvoid *buffer, size_t *lenp, loff_t *ppos)\n--\nipc/ipc_sysctl.c=93=static const struct ctl_table ipc_sysctls[] = {\n--\nipc/ipc_sysctl.c-166-\t\t.mode\t\t= 0644,\nipc/ipc_sysctl.c:167:\t\t.proc_handler\t= proc_ipc_sem_dointvec,\nipc/ipc_sysctl.c-168-\t},\n"
} |
| 25/2 | 2026/10/29 18:13 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 18300 output: 36 thoughts: 22 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience and written in the first person: **Deep Dive into `setup_ipc_sysctls` and `ipc_sysctls` Registration** Okay, so I'm digging into how the IPC system controls are initialized, specifically focusing on `setup_ipc_sysctls` and the registration of the `ipc_sysctls` structure. I need to understand how these knobs are exposed to the user through the `/proc/sys` filesystem or a similar interface, and what underlying mechanisms are employed for their management. My immediate concerns revolve around several key aspects: How is the `ipc_sysctls` structure defined? What data structures does it encapsulate? What sysctl handlers are associated with each tunable parameter? Are these handlers custom-written, or do they leverage a generic framework? I'm also curious about the registration process itself. Where in the kernel's boot or initialization sequence does `setup_ipc_sysctls` get called? Is it a module initialization, or part of the core kernel setup? What's the impact of this registration – does it involve creating new directory entries under `/proc/sys`, allocating kernel memory for sysctl data, or setting up callbacks to handle changes to these parameters? Furthermore, I want to trace the flow of control when a user modifies an IPC sysctl value. How are these modifications propagated to the underlying IPC subsystems (e.g., message queues, semaphores, shared memory)? Are there any synchronization mechanisms employed to ensure data integrity during concurrent accesses? I'll probably need to look at the corresponding sysctl handlers themselves to get a handle on that. Finally, I'm expecting some kind of protection mechanisms - likely access control for these knobs, based on the principle of least privilege. Are there checks for permissions to ensure that only authorized processes can change the IPC settings? Are there any security implications I need to be aware of? I'll need to see how these checks are implemented to determine their effectiveness. Time to get down into the code and see. |
| 26/2 | 2026/10/29 18:13 | tool | read-file |
0mArgs:{
"File": "ipc/ipc_sysctl.c",
"FirstLine": 260,
"LineCount": 55
}Results: {
"Contents": " 260:\t};\n 261:\t\n 262:\tbool setup_ipc_sysctls(struct ipc_namespace *ns)\n 263:\t{\n 264:\t\tstruct ctl_table *tbl;\n 265:\t\n 266:\t\tsetup_sysctl_set(\u0026ns-\u003eipc_set, \u0026set_root, set_is_seen);\n 267:\t\n 268:\t\ttbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL);\n 269:\t\tif (tbl) {\n 270:\t\t\tint i;\n 271:\t\n 272:\t\t\tfor (i = 0; i \u003c ARRAY_SIZE(ipc_sysctls); i++) {\n 273:\t\t\t\tif (tbl[i].data == \u0026init_ipc_ns.shm_ctlmax)\n 274:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlmax;\n 275:\t\n 276:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_ctlall)\n 277:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlall;\n 278:\t\n 279:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_ctlmni)\n 280:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlmni;\n 281:\t\n 282:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_rmid_forced)\n 283:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_rmid_forced;\n 284:\t\n 285:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmax)\n 286:\t\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmax;\n 287:\t\n 288:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmni)\n 289:\t\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmni;\n 290:\t\n 291:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmnb)\n 292:\t\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmnb;\n 293:\t\n 294:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.sem_ctls)\n 295:\t\t\t\t\ttbl[i].data = \u0026ns-\u003esem_ctls;\n 296:\t#ifdef CONFIG_CHECKPOINT_RESTORE\n 297:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_SEM_IDS].next_id)\n 298:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_SEM_IDS].next_id;\n 299:\t\n 300:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_MSG_IDS].next_id)\n 301:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_MSG_IDS].next_id;\n 302:\t\n 303:\t\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_SHM_IDS].next_id)\n 304:\t\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_SHM_IDS].next_id;\n 305:\t#endif\n 306:\t\t\t\telse\n 307:\t\t\t\t\ttbl[i].data = NULL;\n 308:\t\t\t}\n 309:\t\n 310:\t\t\tns-\u003eipc_sysctls = __register_sysctl_table(\u0026ns-\u003eipc_set, \"kernel\", tbl,\n 311:\t\t\t\t\t\t\t\t ARRAY_SIZE(ipc_sysctls));\n 312:\t\t}\n 313:\t\tif (!ns-\u003eipc_sysctls) {\n 314:\t\t\tkfree(tbl);\n"
} |
| 27/2 | 2026/10/29 18:13 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 19818 output: 28 thoughts: 568 Thoughts: **Analyzing IPC Namespace Semaphore Control** Okay, so I'm looking at how semaphore control is managed within an IPC namespace, specifically focusing on the `/proc/sys/kernel/sem` settings. `setup_ipc_sysctls` is the entry point, called during IPC namespace creation, or within `init_ipc_ns`, which is the global initialization. The key seems to be `proc_ipc_sem_dointvec`. I can see it takes a table with `data` and uses `container_of` to get the `ipc_namespace` pointer (`ns`) from the table data. This is smart; it's how they're accessing the namespace-specific semaphore controls. In `init_ipc_ns`, `table->data` is initialized to the address of `init_ipc_ns.sem_ctls` and later `tbl[i].data = &ns->sem_ctls;` in the `setup_ipc_sysctls`. Thus `container_of` correctly gives us the enclosing `ipc_namespace` struct, given the embedded `sem_ctls` within it. Then, there's a temporary buffer, `sem_ctls`, to hold the values. It copies the current semaphore control settings from `ns->sem_ctls`, locks a mutex (`ns->sem_ctls_mutex`), modifies them via `proc_dointvec`, and writes the modified values back to `ns->sem_ctls`. There's also a quick range check, to make sure the values being set are sensible. The lock ensures that concurrent modifications are synchronized. So, I'm pretty sure `proc_ipc_sem_dointvec` is *the* function used for reading and writing `/proc/sys/kernel/sem`. This is important because `semtimedop` and `semop` (which are called by our syscalls) ultimately call `do_semtimedop`. Now, let's trace where `do_semtimedop` is invoked from. That is where we will see the interaction between the system calls and the semaphore values. |
| 28/2 | 2026/10/29 18:13 | tool | grepper |
0mArgs:{
"Expression": "do_semtimedop",
"PathPrefixes": [
"ipc/"
]
}Results: {
"Output": "ipc/sem.c=1907=static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)\n--\nipc/sem.c-1983-\nipc/sem.c:1984:long __do_semtimedop(int semid, struct sembuf *sops,\nipc/sem.c-1985-\t\tunsigned int nsops, const struct timespec64 *timeout,\n--\nipc/sem.c-2222-\nipc/sem.c:2223:static long do_semtimedop(int semid, struct sembuf __user *tsops,\nipc/sem.c-2224-\t\tunsigned int nsops, const struct timespec64 *timeout)\n--\nipc/sem.c-2247-\nipc/sem.c:2248:\tret = __do_semtimedop(semid, sops, nsops, timeout, ns);\nipc/sem.c-2249-\n--\nipc/sem.c=2257=long ksys_semtimedop(int semid, struct sembuf __user *tsops,\n--\nipc/sem.c-2263-\t\t\treturn -EFAULT;\nipc/sem.c:2264:\t\treturn do_semtimedop(semid, tsops, nsops, \u0026ts);\nipc/sem.c-2265-\t}\nipc/sem.c:2266:\treturn do_semtimedop(semid, tsops, nsops, NULL);\nipc/sem.c-2267-}\n--\nipc/sem.c=2276=long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,\n--\nipc/sem.c-2283-\t\t\treturn -EFAULT;\nipc/sem.c:2284:\t\treturn do_semtimedop(semid, tsems, nsops, \u0026ts);\nipc/sem.c-2285-\t}\nipc/sem.c:2286:\treturn do_semtimedop(semid, tsems, nsops, NULL);\nipc/sem.c-2287-}\n--\nipc/sem.c=2297=SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,\n--\nipc/sem.c-2299-{\nipc/sem.c:2300:\treturn do_semtimedop(semid, tsops, nsops, NULL);\nipc/sem.c-2301-}\n"
} |
| 29/2 | 2026/10/29 18:13 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 21501 output: 31 thoughts: 300 Thoughts: **WorthFuzzing: SysV IPC Semaphores** Okay, so `semop` and `semtimedop` are standard SysV IPC system calls. And SysV IPC itself is part of a *core* subsystem. Specifically, it's right there under `ipc/` which falls under syscall handling, and that's definitely a core area, right up there with memory management, locking, and networking. That's good. So, is this even *reachable* in a typical setup? Let's see... Yep! SysV IPC is standard in every Linux distro, QEMU, GCE, even syzkaller. We're talking about things like `sys_semop`, `sys_semtimedop`, and even the procfs sysctl write to `/proc/sys/kernel/sem` and `sem_init_ns`. That's a pretty broad footprint. Alright, what about the *negative* criteria? Is this touching anything non-kernel or non-executable? Nope, all C files and headers. Is it structurally unreachable hardware? Definitely not. Unreachable execution paths? Also no. This code is *definitely* reachable. Therefore, WorthFuzzing is *true*! We've got a winner! Now, the next steps: 1. What configuration options do we need to enable? (EnableConfigs). 2. What specific symbols should we focus on? (FocusSymbols). 3. And, ultimately, what's the detailed reasoning? Time to dig into the Kconfig for `ipc/`. |
| 30/2 | 2026/10/29 18:14 | tool | grepper |
0mArgs:{
"Expression": "ipc_sysctl|sem\\.c",
"PathPrefixes": [
"ipc/"
]
}Results: {
"Output": "ipc/Makefile=7=obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o syscall.o\nipc/Makefile:8:obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o\nipc/Makefile-9-obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o\n--\nipc/ipc_sysctl.c=91=int ipc_min_cycle = RADIX_TREE_MAP_SIZE;\nipc/ipc_sysctl.c-92-\nipc/ipc_sysctl.c:93:static const struct ctl_table ipc_sysctls[] = {\nipc/ipc_sysctl.c-94-\t{\n--\nipc/ipc_sysctl.c=256=static struct ctl_table_root set_root = {\n--\nipc/ipc_sysctl.c-261-\nipc/ipc_sysctl.c:262:bool setup_ipc_sysctls(struct ipc_namespace *ns)\nipc/ipc_sysctl.c-263-{\n--\nipc/ipc_sysctl.c-267-\nipc/ipc_sysctl.c:268:\ttbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL);\nipc/ipc_sysctl.c-269-\tif (tbl) {\n--\nipc/ipc_sysctl.c-271-\nipc/ipc_sysctl.c:272:\t\tfor (i = 0; i \u003c ARRAY_SIZE(ipc_sysctls); i++) {\nipc/ipc_sysctl.c-273-\t\t\tif (tbl[i].data == \u0026init_ipc_ns.shm_ctlmax)\n--\nipc/ipc_sysctl.c-309-\nipc/ipc_sysctl.c:310:\t\tns-\u003eipc_sysctls = __register_sysctl_table(\u0026ns-\u003eipc_set, \"kernel\", tbl,\nipc/ipc_sysctl.c:311:\t\t\t\t\t\t\t ARRAY_SIZE(ipc_sysctls));\nipc/ipc_sysctl.c-312-\t}\nipc/ipc_sysctl.c:313:\tif (!ns-\u003eipc_sysctls) {\nipc/ipc_sysctl.c-314-\t\tkfree(tbl);\n--\nipc/ipc_sysctl.c-321-\nipc/ipc_sysctl.c:322:void retire_ipc_sysctls(struct ipc_namespace *ns)\nipc/ipc_sysctl.c-323-{\n--\nipc/ipc_sysctl.c-325-\nipc/ipc_sysctl.c:326:\ttbl = ns-\u003eipc_sysctls-\u003ectl_table_arg;\nipc/ipc_sysctl.c:327:\tunregister_sysctl_table(ns-\u003eipc_sysctls);\nipc/ipc_sysctl.c-328-\tretire_sysctl_set(\u0026ns-\u003eipc_set);\n--\nipc/ipc_sysctl.c-331-\nipc/ipc_sysctl.c:332:static int __init ipc_sysctl_init(void)\nipc/ipc_sysctl.c-333-{\nipc/ipc_sysctl.c:334:\tif (!setup_ipc_sysctls(\u0026init_ipc_ns)) {\nipc/ipc_sysctl.c-335-\t\tpr_warn(\"ipc sysctl registration failed\\n\");\n--\nipc/ipc_sysctl.c-340-\nipc/ipc_sysctl.c:341:device_initcall(ipc_sysctl_init);\nipc/ipc_sysctl.c-342-\n--\nipc/namespace.c=39=static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,\n--\nipc/namespace.c-80-\nipc/namespace.c:81:\tif (!setup_ipc_sysctls(ns))\nipc/namespace.c-82-\t\tgoto fail_mq_sysctls;\n--\nipc/namespace.c-94-fail_ipc:\nipc/namespace.c:95:\tretire_ipc_sysctls(ns);\nipc/namespace.c-96-fail_mq_sysctls:\n--\nipc/namespace.c=150=static void free_ipc_ns(struct ipc_namespace *ns)\n--\nipc/namespace.c-161-\tretire_mq_sysctls(ns);\nipc/namespace.c:162:\tretire_ipc_sysctls(ns);\nipc/namespace.c-163-\n--\nipc/sem.c-2-/*\nipc/sem.c:3: * linux/ipc/sem.c\nipc/sem.c-4- * Copyright (C) 1992 Krishna Balasubramanian\n"
} |
| 31/2 | 2026/10/29 18:14 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 23382 output: 27 thoughts: 25 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Examining Kconfig for SYSVIPC and SYSVIPC_SYSCTL** Alright, let's dive into the core configuration. My first step is to pull up `init/Kconfig`. I need to understand the configuration options for System V Inter-Process Communication (`SYSVIPC`) and its associated sysctl interface (`SYSVIPC_SYSCTL`). I'm going to quickly scan through this file, focusing on how these options are presented, their dependencies, and any default settings. Specifically, I'm interested in how these options are gated, whether they're mutually exclusive with other IPC mechanisms, and what impact enabling or disabling them has on the broader system functionality. The goal here is to get a baseline understanding of how these features are exposed to the user at configuration time. Any potential conflicts or unusual dependencies need to be flagged immediately. From there I can determine how those settings might interact with whatever I'm troubleshooting. I'll also be watching for any recent changes or commits affecting these particular configurations. |
| 32/2 | 2026/10/29 18:14 | tool | grepper |
0mArgs:{
"Expression": "config SYSVIPC",
"PathPrefixes": [
"init/"
]
}Results: {
"Output": "init/Kconfig=266=config DEFAULT_HOSTNAME\n--\ninit/Kconfig-274-\ninit/Kconfig:275:config SYSVIPC\ninit/Kconfig-276-\tbool \"System V IPC\"\n--\ninit/Kconfig-289-\ninit/Kconfig:290:config SYSVIPC_SYSCTL\ninit/Kconfig-291-\tbool\n--\ninit/Kconfig-295-\ninit/Kconfig:296:config SYSVIPC_COMPAT\ninit/Kconfig-297-\tdef_bool y\n"
} |
| 33/2 | 2026/10/29 18:14 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 23815 output: 32 thoughts: 20 Thoughts: Okay, let's dive into this. I'm going to focus in on lines 270-305 of `init/Kconfig`. I need to understand what configuration options are being presented here and, more importantly, how they relate to the bigger picture of the kernel initialization process. This section is probably key to understanding a specific module or feature. I need to figure out what's being enabled or disabled through these settings. I expect to see dependencies, help text, and default values. My expert eye is looking for any red flags – potential conflicts or oddities in the design – and how they influence the build. Understanding this part of the configuration is crucial for optimizing the kernel for specific hardware or use cases. Let’s see what goodies are in there. |
| 34/2 | 2026/10/29 18:14 | tool | read-file |
0mArgs:{
"File": "init/Kconfig",
"FirstLine": 270,
"LineCount": 35
}Results: {
"Contents": " 270:\t\t This option determines the default system hostname before userspace\n 271:\t\t calls sethostname(2). The kernel traditionally uses \"(none)\" here,\n 272:\t\t but you may wish to use a different default here to make a minimal\n 273:\t\t system more usable with less configuration.\n 274:\t\n 275:\tconfig SYSVIPC\n 276:\t\tbool \"System V IPC\"\n 277:\t\thelp\n 278:\t\t Inter Process Communication is a suite of library functions and\n 279:\t\t system calls which let processes (running programs) synchronize and\n 280:\t\t exchange information. It is generally considered to be a good thing,\n 281:\t\t and some programs won't run unless you say Y here. In particular, if\n 282:\t\t you want to run the DOS emulator dosemu under Linux (read the\n 283:\t\t DOSEMU-HOWTO, available from \u003chttp://www.tldp.org/docs.html#howto\u003e),\n 284:\t\t you'll need to say Y here.\n 285:\t\n 286:\t\t You can find documentation about IPC with \"info ipc\" and also in\n 287:\t\t section 6.4 of the Linux Programmer's Guide, available from\n 288:\t\t \u003chttp://www.tldp.org/guides.html\u003e.\n 289:\t\n 290:\tconfig SYSVIPC_SYSCTL\n 291:\t\tbool\n 292:\t\tdepends on SYSVIPC\n 293:\t\tdepends on SYSCTL\n 294:\t\tdefault y\n 295:\t\n 296:\tconfig SYSVIPC_COMPAT\n 297:\t\tdef_bool y\n 298:\t\tdepends on COMPAT \u0026\u0026 SYSVIPC\n 299:\t\n 300:\tconfig POSIX_MQUEUE\n 301:\t\tbool \"POSIX Message Queues\"\n 302:\t\tdepends on NET\n 303:\t\thelp\n 304:\t\t POSIX variant of message queues is a part of IPC. In POSIX message\n"
} |
| 35/2 | 2026/10/29 18:14 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 24573 output: 184 thoughts: 1078 Thoughts: **Analyzing SysV IPC Semaphore Changes**
Okay, so I'm looking at this patch and immediately, I see we're dealing with `SYSVIPC` and `SYSVIPC_SYSCTL`. `SYSVIPC_SYSCTL` depends on `SYSVIPC` and `SYSCTL`, which makes sense and is enabled by default. So, the configurations involved are these two.
Now, the important part: what's actually being modified? I need to identify the "FocusSymbols" – the entry points or symbols directly impacted by this change. I see a few:
1. `proc_ipc_sem_dointvec`: This is in `ipc/ipc_sysctl.c` and is definitely modified.
2. `do_semtimedop`: This is in `ipc/sem.c` and is a *static* function. I need to figure out if it's inlined or if syscalls like `ksys_semtimedop`, `__x64_sys_semtimedop`, or `__x64_sys_semop` call it. Let's look at `ksys_semtimedop` and `__do_semtimedop`.
Wait a minute, `ksys_semtimedop` calls `do_semtimedop`, and `__do_semtimedop` is called by `do_semtimedop`! So the syscalls that are exposed are `__x64_sys_semtimedop`, `__x64_sys_semop` (or `ksys_semtimedop`).
Hold on a sec - I think I found a bit of an interesting thing about `proc_ipc_sem_dointvec`. Is that static? Yes, but its address is taken in `ipc_sysctls`! So it cannot be inlined by GCC:
```c
{
.procname = "sem",
.data = &init_ipc_ns.sem_ctls,
.maxlen = 4*sizeof(int),
.mode = 0644,
.proc_handler = proc_ipc_sem_dointvec,
},
```
So this definitely means `proc_ipc_sem_dointvec` will be a distinct symbol in the vmlinux image.
3. `sem_init_ns`: This isn't static.
4. `ksys_semtimedop`: This isn't static either.
5. `__do_semtimedop`: This is not static.
6. `do_semtimedop`: This is static, but might or might not be inlined.
So, the key symbols are these, I think: `proc_ipc_sem_dointvec`, `do_semtimedop`, `ksys_semtimedop`, `__do_semtimedop`, and `sem_init_ns`.
Now, are these ubiquitous? No, thankfully. They are very specifically related to SysV IPC semaphores and the `/proc/sys/kernel/sem` sysctl. This means it's not some general memory allocator or a page fault handler or a ubiquitous lock function.
Let's do a final check of the patch's mechanics:
* There's mutex serialization happening for writes to `/proc/sys/kernel/sem` via `ns->sem_ctls_mutex`. Good.
* The `sem_ctls` are copied to a local stack buffer, and it validates conditions like `sem_ctls[2] < 0 || sem_ctls[3] < 0 || sem_ctls[3] > ipc_mni`. Then, the `ns->sem_ctls` is updated via `WRITE_ONCE`. Sounds solid.
* In `do_semtimedop`, `kvmalloc_objs` now includes `GFP_KERNEL_ACCOUNT`.
* The runtime limit of `semopm` has been increased to `INT_MAX`.
Okay, this is a functional logic change and synchronization change within SysV IPC, directly reachable through `semop`, `semtimedop`, and sysctl writes to `/proc/sys/kernel/sem`. This looks like a good candidate for fuzzing. `WorthFuzzing` is definitely true here.
So, the key configs are `SYSVIPC` and `SYSVIPC_SYSCTL`.
And the important symbols, as I've mentioned, are: `proc_ipc_sem_dointvec`, `do_semtimedop`, `ksys_semtimedop`, `__do_semtimedop`, and `sem_init
|
| 36/2 | 2026/10/29 18:15 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"SYSVIPC",
"SYSVIPC_SYSCTL"
],
"FocusSymbols": [
"proc_ipc_sem_dointvec",
"do_semtimedop",
"ksys_semtimedop",
"__do_semtimedop",
"sem_init_ns"
],
"Reasoning": "The patch modifies System V IPC semaphore handling by introducing a mutex to serialize writers to /proc/sys/kernel/sem, validating sem_ctls[2] (semopm) along with semmni, lifting the historical limit on SEMOPM to INT_MAX, and adding GFP_KERNEL_ACCOUNT to kvmalloc_objs in do_semtimedop. These changes modify reachable core IPC syscall handling and sysctl interfaces, warranting fuzzing.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"SYSVIPC",
"SYSVIPC_SYSCTL"
],
"FocusSymbols": [
"proc_ipc_sem_dointvec",
"do_semtimedop",
"ksys_semtimedop",
"__do_semtimedop",
"sem_init_ns"
],
"Reasoning": "The patch modifies System V IPC semaphore handling by introducing a mutex to serialize writers to /proc/sys/kernel/sem, validating sem_ctls[2] (semopm) along with semmni, lifting the historical limit on SEMOPM to INT_MAX, and adding GFP_KERNEL_ACCOUNT to kvmalloc_objs in do_semtimedop. These changes modify reachable core IPC syscall handling and sysctl interfaces, warranting fuzzing.",
"WorthFuzzing": true
} |
| 37/1 | 2026/10/29 18:15 | action | If |
7mArgs:{
"WorthFuzzing": true
}Results: null |
| 38/2 | 2026/10/29 18:15 | agent | kmsan-evaluator |
7mModel:core Args: null Results: {
"KMSANReasoning": "The patch series serializes writes to the sysctl kernel.sem parameter using a new mutex (sem_ctls_mutex), adds validation checks on sem_ctls values, and adds the GFP_KERNEL_ACCOUNT flag to kvmalloc_objs() in do_semtimedop().\n\nKMSAN is not needed because:\n1. The local stack array `sem_ctls` in `proc_ipc_sem_dointvec()` is fully initialized from `ns-\u003esem_ctls` prior to invoking `proc_dointvec()`.\n2. In `do_semtimedop()`, the allocated `sops` array is immediately and fully populated from user space via `copy_from_user()` over the entire requested size (`nsops * sizeof(*tsops)`) before any elements are accessed.\n3. No uninitialized memory is read, branched upon, or leaked to user space.\n4. Concurrency or locking risks involving the newly added mutex are covered by LOCKDEP, and any out-of-bounds or allocation size issues are covered by KASAN.",
"NeedsKMSAN": false
}Instruction: You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.
CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
a comprehensive suite of debugging tools and sanitizers, including KASAN
(out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
(locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
or page allocations) and kernel-to-user memory info-leaks.
Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.
Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.
Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
attributes, ioctl output arguments, socket options, or BPF buffers) where fields
or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
uninitialized bytes of existing buffers.
Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
dereferences, locking deadlocks, or use-after-free bugs (these are already caught
by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.
Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 185a899cb76dd2fbe1ddeb0def8c8c218a00f04f
Author: syz-cluster <triage@syzkaller.com>
Date: Thu Oct 29 18:09:48 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 12faca29bbb9c3..c06568ccfca88f 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -4,6 +4,7 @@
#include <linux/err.h>
#include <linux/idr.h>
+#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/notifier.h>
#include <linux/nsproxy.h>
@@ -31,6 +32,8 @@ struct ipc_ids {
struct ipc_namespace {
struct ipc_ids ids[3];
+ /* Serialize kernel.sem writers. */
+ struct mutex sem_ctls_mutex;
int sem_ctls[4];
int used_sems;
diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index 75aa3b273cd995..d9f961a1592c7b 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -71,16 +71,15 @@ struct seminfo {
* The values has been chosen to be larger than necessary for any
* known configuration.
*
- * SEMOPM should not be increased beyond 1000, otherwise there is the
- * risk that semop()/semtimedop() fails due to kernel memory fragmentation when
- * allocating the sop array.
+ * SEMOPM is the default maximum number of operations per semop() call. The
+ * runtime limit can be changed through /proc/sys/kernel/sem.
*/
#define SEMMNI 32000 /* <= IPCMNI max # of semaphore identifiers */
#define SEMMSL 32000 /* <= INT_MAX max num of semaphores per id */
#define SEMMNS (SEMMNI*SEMMSL) /* <= INT_MAX max # of semaphores in system */
-#define SEMOPM 500 /* <= 1 000 max num of ops per semop call */
+#define SEMOPM 500 /* <= INT_MAX max num of ops per semop call */
#define SEMVMX 32767 /* <= 32767 semaphore maximum value */
#define SEMAEM SEMVMX /* adjust on exit max value */
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index d038d944257f60..0e3608258fe297 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -51,21 +51,38 @@ static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,
static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
+ struct ctl_table ipc_table;
struct ipc_namespace *ns =
container_of(table->data, struct ipc_namespace, sem_ctls);
- int ret, semmni;
+ int sem_ctls[ARRAY_SIZE(ns->sem_ctls)];
+ size_t i;
+ int ret;
+
+ if (!write)
+ return proc_dointvec(table, write, buffer, lenp, ppos);
- semmni = ns->sem_ctls[3];
- ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ mutex_lock(&ns->sem_ctls_mutex);
+ for (i = 0; i < ARRAY_SIZE(sem_ctls); i++)
+ sem_ctls[i] = READ_ONCE(ns->sem_ctls[i]);
- if (!ret)
- ret = sem_check_semmni(ns);
+ ipc_table = *table;
+ ipc_table.data = sem_ctls;
- /*
- * Reset the semmni value if an error happens.
- */
+ ret = proc_dointvec(&ipc_table, write, buffer, lenp, ppos);
if (ret)
- ns->sem_ctls[3] = semmni;
+ goto out_unlock;
+
+ if (sem_ctls[2] < 0 ||
+ sem_ctls[3] < 0 || sem_ctls[3] > ipc_mni) {
+ ret = -ERANGE;
+ goto out_unlock;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(sem_ctls); i++)
+ WRITE_ONCE(ns->sem_ctls[i], sem_ctls[i]);
+
+out_unlock:
+ mutex_unlock(&ns->sem_ctls_mutex);
return ret;
}
diff --git a/ipc/sem.c b/ipc/sem.c
index 5ec41de7e85b2b..098e483ae8d3c1 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -248,6 +248,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
void sem_init_ns(struct ipc_namespace *ns)
{
+ mutex_init(&ns->sem_ctls_mutex);
ns->sc_semmsl = SEMMSL;
ns->sc_semmns = SEMMNS;
ns->sc_semopm = SEMOPM;
@@ -2234,7 +2235,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
return -EINVAL;
if (nsops > SEMOPM_FAST) {
- sops = kvmalloc_objs(*sops, nsops);
+ sops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);
if (sops == NULL)
return -ENOMEM;
}
diff --git a/ipc/util.h b/ipc/util.h
index a55d6cebe6d3b0..51b4efa3d6db01 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -245,15 +245,6 @@ int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
void (*free)(struct ipc_namespace *, struct kern_ipc_perm *));
-static inline int sem_check_semmni(struct ipc_namespace *ns) {
- /*
- * Check semmni range [0, ipc_mni]
- * semmni is the last element of sem_ctls[4] array
- */
- return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > ipc_mni))
- ? -ERANGE : 0;
-}
-
#ifdef CONFIG_COMPAT
#include <linux/compat.h>
struct compat_ipc_perm {
|
| 39/3 | 2026/10/29 18:15 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 3950 output: 27 thoughts: 844 Thoughts: **Analyzing the Patch for Uninitialized Memory Risks**
Okay, let's dive into this patch and see if any KMSAN checks are warranted. My initial assessment hinges on whether this introduces any uninitialized memory vulnerabilities, so I'll be looking specifically for those.
First, I see the addition of a `struct mutex sem_ctls_mutex;` within the `ipc_namespace` structure in `include/linux/ipc_namespace.h`. That's standard mutex initialization, nothing immediately concerning there. Then, an updated comment in `include/uapi/linux/sem.h`, which is unlikely to introduce any new issues.
The core of the change seems to be in `ipc/ipc_sysctl.c`. The `proc_ipc_sem_dointvec()` function has been modified. Alright, let's break this down. In the non-write case, it's a straightforward call to `proc_dointvec` – no concerns there. However, in the *write* case, there are changes.
It locks `ns->sem_ctls_mutex`, which is good. Then, it copies from `ns->sem_ctls` into a local, stack-allocated array called `sem_ctls`. Specifically, this snippet:
```c
for (i = 0; i < ARRAY_SIZE(sem_ctls); i++)
sem_ctls[i] = READ_ONCE(ns->sem_ctls[i]);
```
This is the critical part. Since the patch *reads* into `sem_ctls` before writing, I'm fairly confident that it is properly initialized. `proc_dointvec` is then called with the write flag set. `proc_dointvec` parses the user buffer, and will update `sem_ctls`. Afterwards, it checks the values of `sem_ctls[2]` and `sem_ctls[3]` for validity. Then, it writes the updated values back to `ns->sem_ctls`.
After a quick glance, it appears that `sem_ctls` is completely initialized before being used. Therefore, I don't see any uninitialized memory vulnerabilities in this section.
Moving on, in `ipc/sem.c`, `sem_init_ns` initializes the new mutex. Looks sound. The `do_semtimedop` function has a change. Now, it's adding `GFP_KERNEL_ACCOUNT` to the `kvmalloc_objs` call. This is interesting. I'm going to quickly check `kvmalloc_objs` and `do_semtimedop`. I don't see a potential KMSAN problem at a glance, but let's be sure. I'll use `grepper` or `read-file` to check `do_semtimedop`. I need to review these allocation paths to confirm the usage and potential for uninitialized memory usage.
|
| 40/3 | 2026/10/29 18:15 | tool | grepper |
0mArgs:{
"Expression": "kvmalloc_objs",
"PathPrefixes": [
"ipc/"
]
}Results: {
"Output": "ipc/sem.c=2223=static long do_semtimedop(int semid, struct sembuf __user *tsops,\n--\nipc/sem.c-2237-\tif (nsops \u003e SEMOPM_FAST) {\nipc/sem.c:2238:\t\tsops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);\nipc/sem.c-2239-\t\tif (sops == NULL)\n"
} |
| 41/3 | 2026/10/29 18:15 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 5571 output: 34 thoughts: 19 Thoughts: Here's my analysis of the provided text, rendered in the first person, assuming a high level of expertise: **Diving into the `do_semtimedop` Function** Alright, let's get down to brass tacks. My initial thought is to zero in on `do_semtimedop` within `ipc/sem.c`. That function is the workhorse of semaphore operations with timeouts, so it's a critical component to understand completely. I need to refresh my memory on its exact implementation, the locking it employs, the signal handling it utilizes, and how it interacts with the system calls. This likely means tracing execution from the user space entry point down through all the kernel layers involved. I expect to be looking for race conditions, potential deadlocks, and how this function manages process suspension and resumption when dealing with timed operations. A full understanding is essential, as this is a core building block for any robust concurrent application relying on semaphores. I also want to consider performance implications - how efficiently does it handle the timed waiting, and does it have any known bottlenecks? This is a jumping-off point for a deeper dive. |
| 42/3 | 2026/10/29 18:16 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 2220,
"LineCount": 60
}Results: {
"Contents": "2220:\t\treturn error;\n2221:\t}\n2222:\t\n2223:\tstatic long do_semtimedop(int semid, struct sembuf __user *tsops,\n2224:\t\t\tunsigned int nsops, const struct timespec64 *timeout)\n2225:\t{\n2226:\t\tstruct sembuf fast_sops[SEMOPM_FAST];\n2227:\t\tstruct sembuf *sops = fast_sops;\n2228:\t\tstruct ipc_namespace *ns;\n2229:\t\tint ret;\n2230:\t\n2231:\t\tns = current-\u003ensproxy-\u003eipc_ns;\n2232:\t\tif (nsops \u003e ns-\u003esc_semopm)\n2233:\t\t\treturn -E2BIG;\n2234:\t\tif (nsops \u003c 1)\n2235:\t\t\treturn -EINVAL;\n2236:\t\n2237:\t\tif (nsops \u003e SEMOPM_FAST) {\n2238:\t\t\tsops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);\n2239:\t\t\tif (sops == NULL)\n2240:\t\t\t\treturn -ENOMEM;\n2241:\t\t}\n2242:\t\n2243:\t\tif (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {\n2244:\t\t\tret = -EFAULT;\n2245:\t\t\tgoto out_free;\n2246:\t\t}\n2247:\t\n2248:\t\tret = __do_semtimedop(semid, sops, nsops, timeout, ns);\n2249:\t\n2250:\tout_free:\n2251:\t\tif (sops != fast_sops)\n2252:\t\t\tkvfree(sops);\n2253:\t\n2254:\t\treturn ret;\n2255:\t}\n2256:\t\n2257:\tlong ksys_semtimedop(int semid, struct sembuf __user *tsops,\n2258:\t\t\t unsigned int nsops, const struct __kernel_timespec __user *timeout)\n2259:\t{\n2260:\t\tif (timeout) {\n2261:\t\t\tstruct timespec64 ts;\n2262:\t\t\tif (get_timespec64(\u0026ts, timeout))\n2263:\t\t\t\treturn -EFAULT;\n2264:\t\t\treturn do_semtimedop(semid, tsops, nsops, \u0026ts);\n2265:\t\t}\n2266:\t\treturn do_semtimedop(semid, tsops, nsops, NULL);\n2267:\t}\n2268:\t\n2269:\tSYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,\n2270:\t\t\tunsigned int, nsops, const struct __kernel_timespec __user *, timeout)\n2271:\t{\n2272:\t\treturn ksys_semtimedop(semid, tsops, nsops, timeout);\n2273:\t}\n2274:\t\n2275:\t#ifdef CONFIG_COMPAT_32BIT_TIME\n2276:\tlong compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,\n2277:\t\t\t\t unsigned int nsops,\n2278:\t\t\t\t const struct old_timespec32 __user *timeout)\n2279:\t{\n"
} |
| 43/3 | 2026/10/29 18:16 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 6772 output: 32 thoughts: 180 Thoughts: **Analyzing the Semtimedop Function** Okay, let's break down this `do_semtimedop` function. First, I see that `sops` is allocated with `kvmalloc_objs` using the user-provided `nsops` count and `GFP_KERNEL_ACCOUNT` for memory accounting. Hmm, and then, right away, there's a `copy_from_user` call. It looks like the data for those `nsops` semaphore operations in `sops` is directly populated from user space via `copy_from_user`. So, all `nsops` elements of `sops` are being initialized this way, rather than being explicitly initialized? That's interesting. If the `copy_from_user` operation fails, we jump straight to `out_free:` and `sops` gets freed. Makes sense; cleanup is crucial. But, if `copy_from_user` succeeds, then we call `__do_semtimedop` with the newly populated `sops` data. Wait a second, there's a detail I'm missing. What exactly *are* the four elements of `sem_ctls`? That seems important. Let me do a quick search for `sem_ctls` across the codebase. I need to understand that better to see how this fits into the overall scheme. |
| 44/3 | 2026/10/29 18:17 | tool | grepper |
0mArgs:{
"Expression": "sem_ctls",
"PathPrefixes": [
"ipc/",
"include/"
]
}Results: {
"Output": "include/linux/ipc_namespace.h=32=struct ipc_namespace {\n--\ninclude/linux/ipc_namespace.h-35-\t/* Serialize kernel.sem writers. */\ninclude/linux/ipc_namespace.h:36:\tstruct mutex\tsem_ctls_mutex;\ninclude/linux/ipc_namespace.h:37:\tint\t\tsem_ctls[4];\ninclude/linux/ipc_namespace.h-38-\tint\t\tused_sems;\n--\nipc/ipc_sysctl.c=51=static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\n--\nipc/ipc_sysctl.c-55-\tstruct ipc_namespace *ns =\nipc/ipc_sysctl.c:56:\t\tcontainer_of(table-\u003edata, struct ipc_namespace, sem_ctls);\nipc/ipc_sysctl.c:57:\tint sem_ctls[ARRAY_SIZE(ns-\u003esem_ctls)];\nipc/ipc_sysctl.c-58-\tsize_t i;\n--\nipc/ipc_sysctl.c-63-\nipc/ipc_sysctl.c:64:\tmutex_lock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c:65:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:66:\t\tsem_ctls[i] = READ_ONCE(ns-\u003esem_ctls[i]);\nipc/ipc_sysctl.c-67-\nipc/ipc_sysctl.c-68-\tipc_table = *table;\nipc/ipc_sysctl.c:69:\tipc_table.data = sem_ctls;\nipc/ipc_sysctl.c-70-\n--\nipc/ipc_sysctl.c-74-\nipc/ipc_sysctl.c:75:\tif (sem_ctls[2] \u003c 0 ||\nipc/ipc_sysctl.c:76:\t sem_ctls[3] \u003c 0 || sem_ctls[3] \u003e ipc_mni) {\nipc/ipc_sysctl.c-77-\t\tret = -ERANGE;\n--\nipc/ipc_sysctl.c-80-\nipc/ipc_sysctl.c:81:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:82:\t\tWRITE_ONCE(ns-\u003esem_ctls[i], sem_ctls[i]);\nipc/ipc_sysctl.c-83-\nipc/ipc_sysctl.c-84-out_unlock:\nipc/ipc_sysctl.c:85:\tmutex_unlock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c-86-\treturn ret;\n--\nipc/ipc_sysctl.c=93=static const struct ctl_table ipc_sysctls[] = {\n--\nipc/ipc_sysctl.c-163-\t\t.procname\t= \"sem\",\nipc/ipc_sysctl.c:164:\t\t.data\t\t= \u0026init_ipc_ns.sem_ctls,\nipc/ipc_sysctl.c-165-\t\t.maxlen\t\t= 4*sizeof(int),\n--\nipc/ipc_sysctl.c=262=bool setup_ipc_sysctls(struct ipc_namespace *ns)\n--\nipc/ipc_sysctl.c-293-\nipc/ipc_sysctl.c:294:\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.sem_ctls)\nipc/ipc_sysctl.c:295:\t\t\t\ttbl[i].data = \u0026ns-\u003esem_ctls;\nipc/ipc_sysctl.c-296-#ifdef CONFIG_CHECKPOINT_RESTORE\n--\nipc/sem.c=174=static int sysvipc_sem_proc_show(struct seq_file *s, void *it);\n--\nipc/sem.c-243-\nipc/sem.c:244:#define sc_semmsl\tsem_ctls[0]\nipc/sem.c:245:#define sc_semmns\tsem_ctls[1]\nipc/sem.c:246:#define sc_semopm\tsem_ctls[2]\nipc/sem.c:247:#define sc_semmni\tsem_ctls[3]\nipc/sem.c-248-\nipc/sem.c=249=void sem_init_ns(struct ipc_namespace *ns)\nipc/sem.c-250-{\nipc/sem.c:251:\tmutex_init(\u0026ns-\u003esem_ctls_mutex);\nipc/sem.c-252-\tns-\u003esc_semmsl = SEMMSL;\n"
} |
| 45/3 | 2026/10/29 18:17 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 8479 output: 19 thoughts: 857 Thoughts: **Analyzing the Semaphore Control Changes** Okay, let's break this down. First, I need to remind myself what these `sem_ctls` are. Ah, right: `sc_semmsl` is the maximum semaphores per ID, `sc_semmns` the maximum in the system, `sc_semopm` the maximum operations per `semop` call, and `sc_semmni` the maximum number of semaphore identifiers. Now, looking at the code, I see a significant change in how these `sem_ctls` are handled within `proc_ipc_sem_dointvec`. Before, it looks like the old code was directly accessing `ns->sem_ctls` during the write operation and then calling `sem_check_semmni`. If an error occurred, it would reset `semmni` to the old value. Okay. The newer version is more interesting. It now seems to be copying the `ns->sem_ctls` values into a local `sem_ctls` array. A mutex is acquired, and the `proc_dointvec` function is called on this local copy. A range check is then performed, confirming that `sem_ctls[2]` and `sem_ctls[3]` are within bounds. If these checks pass, then the new values from `sem_ctls` are written back to `ns->sem_ctls` using `WRITE_ONCE`. Finally, the mutex is released. This looks like a solid improvement with the mutex ensuring atomicity for writes. But that's not all. I also see a modification in `ipc/sem.c` related to the semaphore operation structure allocation: `sops = kvmalloc_objs(*sops, nsops, GFP_KERNEL_ACCOUNT);`. Wait, what was `kvmalloc_objs` like previously? It seems like some arguments were added. I need to confirm: Ah, yes, the old code used `kvmalloc_objs(*sops, nsops)` . Now it takes flags! Why was the old call without flags? Let's check the definition of `kvmalloc_objs` to understand this change better. I'll have to dig into that function's definition. |
| 46/3 | 2026/10/29 18:17 | tool | grepper |
0mArgs:{
"Expression": "define kvmalloc_objs"
}Results: {
"Output": "include/linux/slab.h=1073=void *kmalloc_nolock(size_t size, gfp_t gfp_flags, int node);\n--\ninclude/linux/slab.h-1164-\t__alloc_objs(kvmalloc, default_gfp(__VA_ARGS__), typeof(P), 1)\ninclude/linux/slab.h:1165:#define kvmalloc_objs(P, COUNT, ...) \\\ninclude/linux/slab.h-1166-\t__alloc_objs(kvmalloc, default_gfp(__VA_ARGS__), typeof(P), COUNT)\n"
} |
| 47/3 | 2026/10/29 18:17 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 9991 output: 34 thoughts: 1321 Thoughts: **KMSAN Risk Assessment: SEMOPM Increase and Memory Accounting** Okay, so this patch allows `SEMOPM` to be increased up to `INT_MAX` via `sysctl`. This change is pretty straightforward. The primary motivation seems to be to lift the previous limit on the maximum number of operations per `semop()` call, which was likely causing fragmentation issues with the `sop` array. The code uses `GFP_KERNEL_ACCOUNT` when allocating the `sops` array, which makes sense to account for the increased memory usage when large `SEMOPM` values are used. Now, let's carefully assess the potential for introducing or exposing uninitialized memory vulnerabilities, specifically in the context of KMSAN. My understanding is that KMSAN flags issues where kernel structures are exposed to userspace before they are fully initialized, which is a potential security risk. First, let's consider the `/proc/sys/kernel/sem` interface. When reading the values (e.g., via `cat`), the code reads `ns->sem_ctls`, which are initialized in `sem_init_ns` during namespace creation. So, the array `sem_ctls` is always initialized before being exposed to user space. When writing to the proc file, a `sem_ctls` array gets its values either from `READ_ONCE` from the existing namespace values or from the values passed through sysctl. The modified values are then written back to `ns->sem_ctls` after validation. The code ensures these values are always initialized before being used. The `ipc_table` stack variable is copied by value, and then only the data pointer is updated. The descriptor is never sent back to user space. Therefore, the proc interface is safe. Next, I need to look at `semtimedop` and `do_semtimedop`. When the number of operations (`nsops`) is greater than `SEMOPM_FAST`, memory for the `sops` array is allocated using `kvmalloc_objs` with `GFP_KERNEL_ACCOUNT`. Critically, the `sops` array is then populated with data copied *from* userspace using `copy_from_user`. So, if `copy_from_user` fails, then `sops` is freed without being read. If the copy succeeds, all elements within `sops` are overwritten with user-provided values. This seems safe as `copy_from_user` effectively initializes the `sops` array before any kernel functions process it. Checking the code of `__do_semtimedop` does not indicate the presence of any copy to userspace or reads from uninitialized memory. Therefore, I believe the risk here is low. |
| 48/3 | 2026/10/29 18:18 | tool | grepper |
0mArgs:{
"Expression": "static int __do_semtimedop",
"PathPrefixes": [
"ipc/sem.c"
]
}Results: {
"Output": "no matches"
} |
| 49/3 | 2026/10/29 18:18 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11933 output: 32 thoughts: 34 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into Semaphore Operations** Alright, the objective here is clear: pinpoint the location of `__do_semtimedop` or gain a thorough understanding of the semaphore system. My initial instinct is to hone in on the core implementation in `ipc/sem.c`, specifically focusing on the region around lines 2100-2230. This seems like a reasonable starting point, as this area is likely to contain the pivotal logic for semaphore timed operations, given the name `__do_semtimedop`. This is where I would start my investigation. |
| 50/3 | 2026/10/29 18:19 | tool | grepper |
0mArgs:{
"Expression": "__do_semtimedop",
"PathPrefixes": [
"ipc/sem.c"
]
}Results: {
"Output": "ipc/sem.c=1907=static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)\n--\nipc/sem.c-1983-\nipc/sem.c:1984:long __do_semtimedop(int semid, struct sembuf *sops,\nipc/sem.c-1985-\t\tunsigned int nsops, const struct timespec64 *timeout,\n--\nipc/sem.c=2223=static long do_semtimedop(int semid, struct sembuf __user *tsops,\n--\nipc/sem.c-2247-\nipc/sem.c:2248:\tret = __do_semtimedop(semid, sops, nsops, timeout, ns);\nipc/sem.c-2249-\n"
} |
| 51/3 | 2026/10/29 18:19 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12351 output: 34 thoughts: 24 Thoughts: Here's a summary of my thought process, as requested: **Diving into the Semaphore Implementation** Okay, time to get my hands dirty. I need to understand what's going on in the semaphore implementation, specifically around lines 1980 to 2050 in `ipc/sem.c`. I expect these lines likely deal with either a critical section, a system call or a locking mechanism. Given the complexity of inter-process communication, a deeper dive is required to understand the low-level interactions. I'll be looking for any hints on how semaphores manage their state, particularly how they handle contention and wake up waiting processes. I'll need to pay close attention to the data structures involved: are there queueing mechanisms or priority considerations at play? Understanding the flow of execution within that section will illuminate the design choices behind the semaphore's behavior. Hopefully, the surrounding code will provide enough context to infer the intent of this specific piece, or I may need to expand the scope of my investigation. |
| 52/3 | 2026/10/29 18:20 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 1980,
"LineCount": 80
}Results: {
"Contents": "1980:\tout:\n1981:\t\treturn un;\n1982:\t}\n1983:\t\n1984:\tlong __do_semtimedop(int semid, struct sembuf *sops,\n1985:\t\t\tunsigned int nsops, const struct timespec64 *timeout,\n1986:\t\t\tstruct ipc_namespace *ns)\n1987:\t{\n1988:\t\tint error = -EINVAL;\n1989:\t\tstruct sem_array *sma;\n1990:\t\tstruct sembuf *sop;\n1991:\t\tstruct sem_undo *un;\n1992:\t\tint max, locknum;\n1993:\t\tbool undos = false, alter = false, dupsop = false;\n1994:\t\tstruct sem_queue queue;\n1995:\t\tunsigned long dup = 0;\n1996:\t\tktime_t expires, *exp = NULL;\n1997:\t\tbool timed_out = false;\n1998:\t\n1999:\t\tif (nsops \u003c 1 || semid \u003c 0)\n2000:\t\t\treturn -EINVAL;\n2001:\t\tif (nsops \u003e ns-\u003esc_semopm)\n2002:\t\t\treturn -E2BIG;\n2003:\t\n2004:\t\tif (timeout) {\n2005:\t\t\tif (!timespec64_valid(timeout))\n2006:\t\t\t\treturn -EINVAL;\n2007:\t\t\texpires = ktime_add_safe(ktime_get(),\n2008:\t\t\t\t\ttimespec64_to_ktime(*timeout));\n2009:\t\t\texp = \u0026expires;\n2010:\t\t}\n2011:\t\n2012:\t\n2013:\t\tmax = 0;\n2014:\t\tfor (sop = sops; sop \u003c sops + nsops; sop++) {\n2015:\t\t\tunsigned long mask = 1ULL \u003c\u003c ((sop-\u003esem_num) % BITS_PER_LONG);\n2016:\t\n2017:\t\t\tif (sop-\u003esem_num \u003e= max)\n2018:\t\t\t\tmax = sop-\u003esem_num;\n2019:\t\t\tif (sop-\u003esem_flg \u0026 SEM_UNDO)\n2020:\t\t\t\tundos = true;\n2021:\t\t\tif (dup \u0026 mask) {\n2022:\t\t\t\t/*\n2023:\t\t\t\t * There was a previous alter access that appears\n2024:\t\t\t\t * to have accessed the same semaphore, thus use\n2025:\t\t\t\t * the dupsop logic. \"appears\", because the detection\n2026:\t\t\t\t * can only check % BITS_PER_LONG.\n2027:\t\t\t\t */\n2028:\t\t\t\tdupsop = true;\n2029:\t\t\t}\n2030:\t\t\tif (sop-\u003esem_op != 0) {\n2031:\t\t\t\talter = true;\n2032:\t\t\t\tdup |= mask;\n2033:\t\t\t}\n2034:\t\t}\n2035:\t\n2036:\t\tif (undos) {\n2037:\t\t\t/* On success, find_alloc_undo takes the rcu_read_lock */\n2038:\t\t\tun = find_alloc_undo(ns, semid);\n2039:\t\t\tif (IS_ERR(un)) {\n2040:\t\t\t\terror = PTR_ERR(un);\n2041:\t\t\t\tgoto out;\n2042:\t\t\t}\n2043:\t\t} else {\n2044:\t\t\tun = NULL;\n2045:\t\t\trcu_read_lock();\n2046:\t\t}\n2047:\t\n2048:\t\tsma = sem_obtain_object_check(ns, semid);\n2049:\t\tif (IS_ERR(sma)) {\n2050:\t\t\trcu_read_unlock();\n2051:\t\t\terror = PTR_ERR(sma);\n2052:\t\t\tgoto out;\n2053:\t\t}\n2054:\t\n2055:\t\terror = -EFBIG;\n2056:\t\tif (max \u003e= sma-\u003esem_nsems) {\n2057:\t\t\trcu_read_unlock();\n2058:\t\t\tgoto out;\n2059:\t\t}\n"
} |
| 53/3 | 2026/10/29 18:20 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 13721 output: 34 thoughts: 59 Thoughts: Okay, let's dive into this semaphore undo situation. My immediate concern, given my expertise, is the interaction of `sem_undo` with a potentially large `nsops` value, or perhaps the behavior of `find_alloc_undo`. Specifically, I want to confirm if `SEMOPM` has any unexpected consequences with uninitialized memory. To get a clearer picture, I'm going to focus my attention on `find_alloc_undo` within `ipc/sem.c`. That seems like the logical place to start digging deeper. |
| 54/3 | 2026/10/29 18:20 | tool | read-file |
0mArgs:{
"File": "ipc/sem.c",
"FirstLine": 1905,
"LineCount": 80
}Results: {
"Contents": "1905:\t * performs a rcu_read_lock().\n1906:\t */\n1907:\tstatic struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)\n1908:\t{\n1909:\t\tstruct sem_array *sma;\n1910:\t\tstruct sem_undo_list *ulp;\n1911:\t\tstruct sem_undo *un, *new;\n1912:\t\tint nsems, error;\n1913:\t\n1914:\t\terror = get_undo_list(\u0026ulp);\n1915:\t\tif (error)\n1916:\t\t\treturn ERR_PTR(error);\n1917:\t\n1918:\t\trcu_read_lock();\n1919:\t\tspin_lock(\u0026ulp-\u003elock);\n1920:\t\tun = lookup_undo(ulp, semid);\n1921:\t\tspin_unlock(\u0026ulp-\u003elock);\n1922:\t\tif (likely(un != NULL))\n1923:\t\t\tgoto out;\n1924:\t\n1925:\t\t/* no undo structure around - allocate one. */\n1926:\t\t/* step 1: figure out the size of the semaphore array */\n1927:\t\tsma = sem_obtain_object_check(ns, semid);\n1928:\t\tif (IS_ERR(sma)) {\n1929:\t\t\trcu_read_unlock();\n1930:\t\t\treturn ERR_CAST(sma);\n1931:\t\t}\n1932:\t\n1933:\t\tnsems = sma-\u003esem_nsems;\n1934:\t\tif (!ipc_rcu_getref(\u0026sma-\u003esem_perm)) {\n1935:\t\t\trcu_read_unlock();\n1936:\t\t\tun = ERR_PTR(-EIDRM);\n1937:\t\t\tgoto out;\n1938:\t\t}\n1939:\t\trcu_read_unlock();\n1940:\t\n1941:\t\t/* step 2: allocate new undo structure */\n1942:\t\tnew = kvzalloc_flex(*new, semadj, nsems, GFP_KERNEL_ACCOUNT);\n1943:\t\tif (!new) {\n1944:\t\t\tipc_rcu_putref(\u0026sma-\u003esem_perm, sem_rcu_free);\n1945:\t\t\treturn ERR_PTR(-ENOMEM);\n1946:\t\t}\n1947:\t\n1948:\t\t/* step 3: Acquire the lock on semaphore array */\n1949:\t\trcu_read_lock();\n1950:\t\tsem_lock_and_putref(sma);\n1951:\t\tif (!ipc_valid_object(\u0026sma-\u003esem_perm)) {\n1952:\t\t\tsem_unlock(sma, -1);\n1953:\t\t\trcu_read_unlock();\n1954:\t\t\tkvfree(new);\n1955:\t\t\tun = ERR_PTR(-EIDRM);\n1956:\t\t\tgoto out;\n1957:\t\t}\n1958:\t\tspin_lock(\u0026ulp-\u003elock);\n1959:\t\n1960:\t\t/*\n1961:\t\t * step 4: check for races: did someone else allocate the undo struct?\n1962:\t\t */\n1963:\t\tun = lookup_undo(ulp, semid);\n1964:\t\tif (un) {\n1965:\t\t\tspin_unlock(\u0026ulp-\u003elock);\n1966:\t\t\tkvfree(new);\n1967:\t\t\tgoto success;\n1968:\t\t}\n1969:\t\t/* step 5: initialize \u0026 link new undo structure */\n1970:\t\tnew-\u003eulp = ulp;\n1971:\t\tnew-\u003esemid = semid;\n1972:\t\tassert_spin_locked(\u0026ulp-\u003elock);\n1973:\t\tlist_add_rcu(\u0026new-\u003elist_proc, \u0026ulp-\u003elist_proc);\n1974:\t\tipc_assert_locked_object(\u0026sma-\u003esem_perm);\n1975:\t\tlist_add(\u0026new-\u003elist_id, \u0026sma-\u003elist_id);\n1976:\t\tun = new;\n1977:\t\tspin_unlock(\u0026ulp-\u003elock);\n1978:\tsuccess:\n1979:\t\tsem_unlock(sma, -1);\n1980:\tout:\n1981:\t\treturn un;\n1982:\t}\n1983:\t\n1984:\tlong __do_semtimedop(int semid, struct sembuf *sops,\n"
} |
| 55/3 | 2026/10/29 18:20 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15099 output: 31 thoughts: 103 Thoughts: Okay, here's my breakdown of what's going through my mind as I analyze this: **Investigating Potential Data Leakage in Semaphore Control Structures** Right, so we're seeing `kvzalloc_flex` being used to allocate a new structure, likely a semaphore control block or something similar, and it's being zeroed out. Good, that’s standard practice for security reasons. Now, my immediate concern is, are we leaking any potentially sensitive data via IPC calls? This looks like a kernel-level allocation, so the next thing I'd do is hunt for where this new structure, or parts of it, gets exposed to user space. Specifically, I need to look at IPC commands like `SEMCTL` and see if they copy the contents of the newly zeroed structure. I should also check any sysctl interfaces related to semaphores and see if they're returning this `sem_ctls` data, or a similar data structure like `seminfo`. My main question: Where is `sem_ctls` or something related being *read* or *copied* to user space? I know the allocation is zeroed, but I need to make sure subsequent writes don't inadvertently expose kernel-side data. To do this, I'm going to start a focused search. I'll scan the `ipc/` directory, looking for any references to `sem_ctls` or potentially related variables like `sc_sem` (or similar prefixes). That should quickly identify the relevant code paths. The objective is to identify any potential vulnerabilities related to unintentional data leakage from this new memory block. |
| 56/3 | 2026/10/29 18:21 | tool | grepper |
0mArgs:{
"Expression": "sc_sem|sem_ctls",
"PathPrefixes": [
"ipc/"
]
}Results: {
"Output": "ipc/ipc_sysctl.c=51=static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,\n--\nipc/ipc_sysctl.c-55-\tstruct ipc_namespace *ns =\nipc/ipc_sysctl.c:56:\t\tcontainer_of(table-\u003edata, struct ipc_namespace, sem_ctls);\nipc/ipc_sysctl.c:57:\tint sem_ctls[ARRAY_SIZE(ns-\u003esem_ctls)];\nipc/ipc_sysctl.c-58-\tsize_t i;\n--\nipc/ipc_sysctl.c-63-\nipc/ipc_sysctl.c:64:\tmutex_lock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c:65:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:66:\t\tsem_ctls[i] = READ_ONCE(ns-\u003esem_ctls[i]);\nipc/ipc_sysctl.c-67-\nipc/ipc_sysctl.c-68-\tipc_table = *table;\nipc/ipc_sysctl.c:69:\tipc_table.data = sem_ctls;\nipc/ipc_sysctl.c-70-\n--\nipc/ipc_sysctl.c-74-\nipc/ipc_sysctl.c:75:\tif (sem_ctls[2] \u003c 0 ||\nipc/ipc_sysctl.c:76:\t sem_ctls[3] \u003c 0 || sem_ctls[3] \u003e ipc_mni) {\nipc/ipc_sysctl.c-77-\t\tret = -ERANGE;\n--\nipc/ipc_sysctl.c-80-\nipc/ipc_sysctl.c:81:\tfor (i = 0; i \u003c ARRAY_SIZE(sem_ctls); i++)\nipc/ipc_sysctl.c:82:\t\tWRITE_ONCE(ns-\u003esem_ctls[i], sem_ctls[i]);\nipc/ipc_sysctl.c-83-\nipc/ipc_sysctl.c-84-out_unlock:\nipc/ipc_sysctl.c:85:\tmutex_unlock(\u0026ns-\u003esem_ctls_mutex);\nipc/ipc_sysctl.c-86-\treturn ret;\n--\nipc/ipc_sysctl.c=93=static const struct ctl_table ipc_sysctls[] = {\n--\nipc/ipc_sysctl.c-163-\t\t.procname\t= \"sem\",\nipc/ipc_sysctl.c:164:\t\t.data\t\t= \u0026init_ipc_ns.sem_ctls,\nipc/ipc_sysctl.c-165-\t\t.maxlen\t\t= 4*sizeof(int),\n--\nipc/ipc_sysctl.c=262=bool setup_ipc_sysctls(struct ipc_namespace *ns)\n--\nipc/ipc_sysctl.c-293-\nipc/ipc_sysctl.c:294:\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.sem_ctls)\nipc/ipc_sysctl.c:295:\t\t\t\ttbl[i].data = \u0026ns-\u003esem_ctls;\nipc/ipc_sysctl.c-296-#ifdef CONFIG_CHECKPOINT_RESTORE\n--\nipc/sem.c=174=static int sysvipc_sem_proc_show(struct seq_file *s, void *it);\n--\nipc/sem.c-243-\nipc/sem.c:244:#define sc_semmsl\tsem_ctls[0]\nipc/sem.c:245:#define sc_semmns\tsem_ctls[1]\nipc/sem.c:246:#define sc_semopm\tsem_ctls[2]\nipc/sem.c:247:#define sc_semmni\tsem_ctls[3]\nipc/sem.c-248-\nipc/sem.c=249=void sem_init_ns(struct ipc_namespace *ns)\nipc/sem.c-250-{\nipc/sem.c:251:\tmutex_init(\u0026ns-\u003esem_ctls_mutex);\nipc/sem.c:252:\tns-\u003esc_semmsl = SEMMSL;\nipc/sem.c:253:\tns-\u003esc_semmns = SEMMNS;\nipc/sem.c:254:\tns-\u003esc_semopm = SEMOPM;\nipc/sem.c:255:\tns-\u003esc_semmni = SEMMNI;\nipc/sem.c-256-\tns-\u003eused_sems = 0;\n--\nipc/sem.c=532=static int newary(struct ipc_namespace *ns, struct ipc_params *params)\n--\nipc/sem.c-542-\t\treturn -EINVAL;\nipc/sem.c:543:\tif (ns-\u003eused_sems + nsems \u003e ns-\u003esc_semmns)\nipc/sem.c-544-\t\treturn -ENOSPC;\n--\nipc/sem.c-574-\t/* ipc_addid() locks sma upon success. */\nipc/sem.c:575:\tretval = ipc_addid(\u0026sem_ids(ns), \u0026sma-\u003esem_perm, ns-\u003esc_semmni);\nipc/sem.c-576-\tif (retval \u003c 0) {\n--\nipc/sem.c=603=long ksys_semget(key_t key, int nsems, int semflg)\n--\nipc/sem.c-614-\nipc/sem.c:615:\tif (nsems \u003c 0 || nsems \u003e ns-\u003esc_semmsl)\nipc/sem.c-616-\t\treturn -EINVAL;\n--\nipc/sem.c=1309=static int semctl_info(struct ipc_namespace *ns, int semid,\n--\nipc/sem.c-1320-\tmemset(\u0026seminfo, 0, sizeof(seminfo));\nipc/sem.c:1321:\tseminfo.semmni = ns-\u003esc_semmni;\nipc/sem.c:1322:\tseminfo.semmns = ns-\u003esc_semmns;\nipc/sem.c:1323:\tseminfo.semmsl = ns-\u003esc_semmsl;\nipc/sem.c:1324:\tseminfo.semopm = ns-\u003esc_semopm;\nipc/sem.c-1325-\tseminfo.semvmx = SEMVMX;\n--\nipc/sem.c=1984=long __do_semtimedop(int semid, struct sembuf *sops,\n--\nipc/sem.c-2000-\t\treturn -EINVAL;\nipc/sem.c:2001:\tif (nsops \u003e ns-\u003esc_semopm)\nipc/sem.c-2002-\t\treturn -E2BIG;\n--\nipc/sem.c=2223=static long do_semtimedop(int semid, struct sembuf __user *tsops,\n--\nipc/sem.c-2231-\tns = current-\u003ensproxy-\u003eipc_ns;\nipc/sem.c:2232:\tif (nsops \u003e ns-\u003esc_semopm)\nipc/sem.c-2233-\t\treturn -E2BIG;\n"
} |
| 57/3 | 2026/10/29 18:21 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 17444 output: 19 thoughts: 1034 Thoughts: **Analyzing IPC Semaphore Control Parameter Handling** Okay, let's break this down. First, I see the `semctl_info` function is straightforward; it initializes a structure, `seminfo`, by setting all its fields. Then, my focus is on how the semaphore control parameters are handled, specifically by `proc_ipc_sem_dointvec`. I need to understand this `proc_ipc_sem_dointvec` function in detail. Alright, I see this `proc_ipc_sem_dointvec` function is called. If it's a write operation, there's a mutex protecting access to the `ns->sem_ctls` array. First, it copies the current values of `ns->sem_ctls` into a local array, `sem_ctls`. Then, a local copy of the `ctl_table` is made and its data pointer is updated to point to this local `sem_ctls` array. The key here is to determine whether uninitialized data is in play. The array is initialized: the loop `for (i = 0; i < ARRAY_SIZE(sem_ctls); i++) sem_ctls[i] = READ_ONCE(ns->sem_ctls[i]);` ensures that the local array `sem_ctls` is populated from the current values of the shared `ns->sem_ctls`. The `proc_dointvec` function is then called. With `write = 1`, this reads values from the userspace `buffer` into the `sem_ctls` array. After the call, `sem_ctls[2]` and `sem_ctls[3]` are validated for range. Finally, the new values from the local array are written back to the shared `ns->sem_ctls` array. If it's a read operation, the situation is even simpler: `proc_dointvec` is called with the original `table` structure; that `table->data` originally pointed to `ns->sem_ctls`. This means that reading the `/proc/sys/kernel/sem` entry directly accesses the initialized values from the `ns->sem_ctls` array. Therefore, the array `sem_ctls` is always initialized by either reading the existing values on a write operation, or when calling `READ_ONCE`, and so any vulnerability stemming from uninitialized data is avoided. Also, since there is a mutex used to protect read/write to the parameters, there are no race conditions. I need to confirm that `ns->sem_ctls_mutex` is initialized when the `ipc_namespace` is created and I'm good. Let's trace back where `sem_init_ns` is called to verify this. |
| 58/3 | 2026/10/29 18:22 | tool | grepper |
0mArgs:{
"Expression": "sem_init_ns"
}Results: {
"Output": "ipc/namespace.c=39=static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,\n--\nipc/namespace.c-87-\nipc/namespace.c:88:\tsem_init_ns(ns);\nipc/namespace.c-89-\tshm_init_ns(ns);\n--\nipc/sem.c=174=static int sysvipc_sem_proc_show(struct seq_file *s, void *it);\n--\nipc/sem.c-248-\nipc/sem.c:249:void sem_init_ns(struct ipc_namespace *ns)\nipc/sem.c-250-{\n--\nipc/sem.c=269=void __init sem_init(void)\nipc/sem.c-270-{\nipc/sem.c:271:\tsem_init_ns(\u0026init_ipc_ns);\nipc/sem.c-272-\tipc_init_proc_interface(\"sysvipc/sem\",\n--\nipc/util.h=61=static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }\n--\nipc/util.h-64-#ifdef CONFIG_SYSVIPC\nipc/util.h:65:void sem_init_ns(struct ipc_namespace *ns);\nipc/util.h-66-int msg_init_ns(struct ipc_namespace *ns);\n--\nipc/util.h=71=void shm_exit_ns(struct ipc_namespace *ns);\nipc/util.h-72-#else\nipc/util.h:73:static inline void sem_init_ns(struct ipc_namespace *ns) { }\nipc/util.h-74-static inline int msg_init_ns(struct ipc_namespace *ns) { return 0; }\n"
} |
| 59/3 | 2026/10/29 18:22 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 19545 output: 253 thoughts: 1764 Thoughts: **KMSAN Assessment: No Need for KMSAN** Okay, let's break this down. My initial thought process focused on the changes in this patch and whether they introduce any new risks of uninitialized memory reads or leaks. `sem_init_ns` always initializes the mutex, so that's good. Now, diving into `do_semtimedop`, the key area is the allocation and copy from userspace: the allocation uses `kvmalloc_objs`, and that allocation *is* immediately populated via `copy_from_user`. There's no uninitialized read there, and the memory's size calculation is protected by checks in `kvmalloc_objs` and KASAN will catch overflows. I reviewed the KMSAN guidelines, and based on those, I can confidently say that NeedsKMSAN should be set to `false`. Let's clarify why, step by step: 1. **Mutex Serialization:** The patch introduces a mutex, `sem_ctls_mutex`, to serialize writes to the `kernel.sem` sysctl. This mutex is initialized using `mutex_init`, and any issues (deadlocks, uninitialized mutex, etc.) will be caught by LOCKDEP and DEBUG\_MUTEXES. 2. **Sysctl Interaction:** The `sem_ctls` array is local and temporary within `proc_ipc_sem_dointvec`. It's explicitly initialized by reading the values into it, no uninitialized reads here. Any data read is completely checked and copied back via `WRITE_ONCE`. 3. **`do_semtimedop` Allocation and Copy:** The allocation in `do_semtimedop` now uses `GFP_KERNEL_ACCOUNT`. Critically, `copy_from_user` immediately populates the allocated buffer. There's zero chance of accessing uninitialized data because the entire `nsops * sizeof(*tsops)` bytes are populated before being used. KASAN would catch any out-of-bounds access. 4. **`SEMOPM` Comment and Validation:** The changes to the `SEMOPM` upper bound, including the adjustment to use a check of `sem_ctls[2] < 0`, do not introduce uninitialized memory paths. Therefore, this patch does not introduce any risks related to uninitialized memory. The code operates safely with fully initialized data. Concurrency issues are addressed with LOCKDEP, and any other bugs like out-of-bounds or allocation size issues are handled by KASAN. We are good. |
| 60/3 | 2026/10/29 18:23 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch series serializes writes to the sysctl kernel.sem parameter using a new mutex (sem_ctls_mutex), adds validation checks on sem_ctls values, and adds the GFP_KERNEL_ACCOUNT flag to kvmalloc_objs() in do_semtimedop().\n\nKMSAN is not needed because:\n1. The local stack array `sem_ctls` in `proc_ipc_sem_dointvec()` is fully initialized from `ns-\u003esem_ctls` prior to invoking `proc_dointvec()`.\n2. In `do_semtimedop()`, the allocated `sops` array is immediately and fully populated from user space via `copy_from_user()` over the entire requested size (`nsops * sizeof(*tsops)`) before any elements are accessed.\n3. No uninitialized memory is read, branched upon, or leaked to user space.\n4. Concurrency or locking risks involving the newly added mutex are covered by LOCKDEP, and any out-of-bounds or allocation size issues are covered by KASAN.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch series serializes writes to the sysctl kernel.sem parameter using a new mutex (sem_ctls_mutex), adds validation checks on sem_ctls values, and adds the GFP_KERNEL_ACCOUNT flag to kvmalloc_objs() in do_semtimedop().\n\nKMSAN is not needed because:\n1. The local stack array `sem_ctls` in `proc_ipc_sem_dointvec()` is fully initialized from `ns-\u003esem_ctls` prior to invoking `proc_dointvec()`.\n2. In `do_semtimedop()`, the allocated `sops` array is immediately and fully populated from user space via `copy_from_user()` over the entire requested size (`nsops * sizeof(*tsops)`) before any elements are accessed.\n3. No uninitialized memory is read, branched upon, or leaked to user space.\n4. Concurrency or locking risks involving the newly added mutex are covered by LOCKDEP, and any out-of-bounds or allocation size issues are covered by KASAN.",
"NeedsKMSAN": false
} |
| Total Calls | Total Tokens | Avg Tokens | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|
| Total Calls | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|