AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "KMSANReasoning": "",
  "NeedsKMSAN": false,
  "Reasoning": "The patch only modifies KVM selftests code under tools/testing/selftests/kvm/, which is user-space test code and does not affect the compiled kernel image (vmlinux) or kernel modules.",
  "WorthFuzzing": false
}

null

{
  "PatchDiff": "commit 4edb902cbeadaacbda9e7657aba16bcb978046c0\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Sep 30 23:41:48 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h\nindex 3a432499b3387..9ea5b8906dd4d 100644\n--- a/tools/testing/selftests/kvm/include/test_util.h\n+++ b/tools/testing/selftests/kvm/include/test_util.h\n@@ -238,7 +238,17 @@ static inline u32 atoi_non_negative(const char *name, const char *num_str)\n }\n \n int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args);\n-__printf(3, 4) int guest_snprintf(char *buf, int n, const char *fmt, ...);\n+\n+#define guest_snprintf(__buf, __n, __fmt)\t\t\\\n+({\t\t\t\t\t\t\t\\\n+\tva_list va;\t\t\t\t\t\\\n+\tint len;\t\t\t\t\t\\\n+\t\t\t\t\t\t\t\\\n+\tva_start(va, __fmt);\t\t\t\t\\\n+\tlen = guest_vsnprintf(__buf, __n, __fmt, va);\t\\\n+\tva_end(va);\t\t\t\t\t\\\n+\tlen;\t\t\t\t\t\t\\\n+})\n \n char *strdup_printf(const char *fmt, ...) __attribute__((format(printf, 1, 2), nonnull(1)));\n \ndiff --git a/tools/testing/selftests/kvm/lib/guest_sprintf.c b/tools/testing/selftests/kvm/lib/guest_sprintf.c\nindex 7a33965349a7f..6caebb456f3da 100644\n--- a/tools/testing/selftests/kvm/lib/guest_sprintf.c\n+++ b/tools/testing/selftests/kvm/lib/guest_sprintf.c\n@@ -300,15 +300,3 @@ int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args)\n \t*str = '\\0';\n \treturn str - buf;\n }\n-\n-int guest_snprintf(char *buf, int n, const char *fmt, ...)\n-{\n-\tva_list va;\n-\tint len;\n-\n-\tva_start(va, fmt);\n-\tlen = guest_vsnprintf(buf, n, fmt, va);\n-\tva_end(va);\n-\n-\treturn len;\n-}\ndiff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c\nindex 029ce21f9f2fa..e9df711973678 100644\n--- a/tools/testing/selftests/kvm/lib/ucall_common.c\n+++ b/tools/testing/selftests/kvm/lib/ucall_common.c\n@@ -83,7 +83,6 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,\n \t\t  unsigned int line, const char *fmt, ...)\n {\n \tstruct ucall *uc;\n-\tva_list va;\n \n \tuc = ucall_alloc();\n \tuc-\u003ecmd = cmd;\n@@ -92,9 +91,7 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,\n \tWRITE_ONCE(uc-\u003eargs[GUEST_FILE], (u64)(file));\n \tWRITE_ONCE(uc-\u003eargs[GUEST_LINE], line);\n \n-\tva_start(va, fmt);\n-\tguest_vsnprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt, va);\n-\tva_end(va);\n+\tguest_snprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt);\n \n \tucall_arch_do_ucall((gva_t)uc-\u003ehva);\n \n@@ -104,14 +101,11 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,\n void ucall_fmt(u64 cmd, const char *fmt, ...)\n {\n \tstruct ucall *uc;\n-\tva_list va;\n \n \tuc = ucall_alloc();\n \tuc-\u003ecmd = cmd;\n \n-\tva_start(va, fmt);\n-\tguest_vsnprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt, va);\n-\tva_end(va);\n+\tguest_snprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt);\n \n \tucall_arch_do_ucall((gva_t)uc-\u003ehva);\n \n"
}

core

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch only modifies KVM selftests code under tools/testing/selftests/kvm/, which is user-space test code and does not affect the compiled kernel image (vmlinux) or kernel modules.",
  "WorthFuzzing": false
}

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.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 4edb902cbeadaacbda9e7657aba16bcb978046c0
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Sep 30 23:41:48 2026 +0000

    syz-cluster: applied patch under review

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index 3a432499b3387..9ea5b8906dd4d 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -238,7 +238,17 @@ static inline u32 atoi_non_negative(const char *name, const char *num_str)
 }
 
 int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args);
-__printf(3, 4) int guest_snprintf(char *buf, int n, const char *fmt, ...);
+
+#define guest_snprintf(__buf, __n, __fmt)		\
+({							\
+	va_list va;					\
+	int len;					\
+							\
+	va_start(va, __fmt);				\
+	len = guest_vsnprintf(__buf, __n, __fmt, va);	\
+	va_end(va);					\
+	len;						\
+})
 
 char *strdup_printf(const char *fmt, ...) __attribute__((format(printf, 1, 2), nonnull(1)));
 
diff --git a/tools/testing/selftests/kvm/lib/guest_sprintf.c b/tools/testing/selftests/kvm/lib/guest_sprintf.c
index 7a33965349a7f..6caebb456f3da 100644
--- a/tools/testing/selftests/kvm/lib/guest_sprintf.c
+++ b/tools/testing/selftests/kvm/lib/guest_sprintf.c
@@ -300,15 +300,3 @@ int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args)
 	*str = '\0';
 	return str - buf;
 }
-
-int guest_snprintf(char *buf, int n, const char *fmt, ...)
-{
-	va_list va;
-	int len;
-
-	va_start(va, fmt);
-	len = guest_vsnprintf(buf, n, fmt, va);
-	va_end(va);
-
-	return len;
-}
diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
index 029ce21f9f2fa..e9df711973678 100644
--- a/tools/testing/selftests/kvm/lib/ucall_common.c
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -83,7 +83,6 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,
 		  unsigned int line, const char *fmt, ...)
 {
 	struct ucall *uc;
-	va_list va;
 
 	uc = ucall_alloc();
 	uc->cmd = cmd;
@@ -92,9 +91,7 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,
 	WRITE_ONCE(uc->args[GUEST_FILE], (u64)(file));
 	WRITE_ONCE(uc->args[GUEST_LINE], line);
 
-	va_start(va, fmt);
-	guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
-	va_end(va);
+	guest_snprintf(uc->buffer, UCALL_BUFFER_LEN, fmt);
 
 	ucall_arch_do_ucall((gva_t)uc->hva);
 
@@ -104,14 +101,11 @@ void ucall_assert(u64 cmd, const char *exp, const char *file,
 void ucall_fmt(u64 cmd, const char *fmt, ...)
 {
 	struct ucall *uc;
-	va_list va;
 
 	uc = ucall_alloc();
 	uc->cmd = cmd;
 
-	va_start(va, fmt);
-	guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
-	va_end(va);
+	guest_snprintf(uc->buffer, UCALL_BUFFER_LEN, fmt);
 
 	ucall_arch_do_ucall((gva_t)uc->hva);
 

gemini-3.8-flash

null

null

							input: 3862
							output: 34
							thoughts: 357
						

**WorthFuzzing Triage: Negative Criteria Met**

Okay, here's what I'm thinking. This patch diff is touching files in `tools/testing/selftests/kvm/`: specifically `test_util.h`, `guest_sprintf.c`, and `ucall_common.c`. All right there, under that same directory structure. So, time to apply the triage criteria. Let's see...

I know that the triage philosophy outlines some negative criteria. The second point, specifically. And it says we should set `WorthFuzzing` to `false` *only* if *all* the modified code falls into certain categories. The key point here is that if all the changed files reside in a self-test directory, and does not affect vmlinux or kernel modules, then it's a no-go for fuzzing.

Let's apply that.  `tools/testing/selftests/kvm/` falls squarely under that negative criterion. It's user-space, part of the `tools/` directory.  These are self-tests.  Nothing compiled into the kernel image or kernel modules. Therefore, this change is not relevant for fuzzing and `WorthFuzzing` has to be `false`.

Let's just take a quick peek at the commit and see if there are any other files, just to be sure...

{
  "Expression": "guest_snprintf",
  "PathPrefix": "tools/testing/selftests/kvm"
}

{
  "Output": "tools/testing/selftests/kvm/include/test_util.h=240=int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args);\ntools/testing/selftests/kvm/include/test_util.h-241-\ntools/testing/selftests/kvm/include/test_util.h:242:#define guest_snprintf(__buf, __n, __fmt)\t\t\\\ntools/testing/selftests/kvm/include/test_util.h-243-({\t\t\t\t\t\t\t\\\n--\ntools/testing/selftests/kvm/lib/ucall_common.c=82=void ucall_assert(u64 cmd, const char *exp, const char *file,\n--\ntools/testing/selftests/kvm/lib/ucall_common.c-93-\ntools/testing/selftests/kvm/lib/ucall_common.c:94:\tguest_snprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt);\ntools/testing/selftests/kvm/lib/ucall_common.c-95-\n--\ntools/testing/selftests/kvm/lib/ucall_common.c=101=void ucall_fmt(u64 cmd, const char *fmt, ...)\n--\ntools/testing/selftests/kvm/lib/ucall_common.c-107-\ntools/testing/selftests/kvm/lib/ucall_common.c:108:\tguest_snprintf(uc-\u003ebuffer, UCALL_BUFFER_LEN, fmt);\ntools/testing/selftests/kvm/lib/ucall_common.c-109-\n"
}

gemini-3.8-flash

null

null

							input: 4979
							output: 77
							thoughts: 88
						

Okay, here's my understanding, framed as my internal thought process:

**KVM Selftest Modification Analysis**

Alright, so the key here is the scope. The analysis immediately flags a very specific focus: *only* tools, testing, selftests, and kvm files have been modified. That's the boundary. Let's call this snapshot of the state `set-results`.

`set-results` is a handy label to give to this situation to make it easier to talk about.

Now, for `set-results`, we determine:

*   **`WorthFuzzing: false`**. Since the patch is contained within the user-space testing environment and doesn't touch the kernel image (vmlinux) or any loadable kernel modules, there's no immediate risk of introducing kernel-level vulnerabilities or behavior that would justify fuzzing the kernel itself. This patch does not have any obvious security implications.
*   **`FocusSymbols: []`**. No specific kernel symbols are targeted or modified, at least from what this initial look reveals. The changes are entirely within the user-space testing realm. This confirms our initial observation.
*   **`EnableConfigs: []`**. The code doesn't impact any kernel configuration options. Nothing new needs to be enabled or disabled in the kernel configuration as a result of this patch.
*   **`Reasoning: The patch only modifies KVM selftests user-space code under tools/testing/selftests/kvm/ and does not affect the compiled kernel image (vmlinux) or kernel modules.`** The reasoning is pretty straightforward: It's all confined to the user-space selftest environment. This makes the conclusions pretty clear. We're dealing with test code within the KVM infrastructure, isolated from the core kernel itself.

{
  "EnableConfigs": [],
  "FocusSymbols": [],
  "Reasoning": "The patch only modifies KVM selftests code under tools/testing/selftests/kvm/, which is user-space test code and does not affect the compiled kernel image (vmlinux) or kernel modules.",
  "WorthFuzzing": false
}

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch only modifies KVM selftests code under tools/testing/selftests/kvm/, which is user-space test code and does not affect the compiled kernel image (vmlinux) or kernel modules.",
  "WorthFuzzing": false
}

{
  "WorthFuzzing": false
}

null