| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/09/08 21:09 | flow | patch-triage |
1mArgs:null Results: {
"EnableConfigs": [
"MPTCP"
],
"FocusSymbols": [
"mptcp_subflow_reqsk_clone",
"mptcp_token_move_request",
"mptcp_token_accept",
"mptcp_token_destroy_request",
"mptcp_sk_clone_init",
"subflow_syn_recv_sock",
"inet_reqsk_clone"
],
"KMSANReasoning": "The patch fixes MPTCP request socket cloning during reuseport socket migration by safely handling msk socket refcounts, moving token hash table entries (mptcp_token_move_request), and properly cleaning up and falling back when mptcp_token_accept fails.\n\nThese changes involve concurrency, RCU safety, socket refcounting, and lifecycle/destruction state management. Any potential bugs in this area are use-after-free, refcounting issues, or locking/deadlock bugs, which are detected by KASAN, LOCKDEP, and standard kernel sanitizers. The patch does not introduce or modify uninitialized stack/heap allocations, memory copying to userspace, padding/info-leaks, or branching on uninitialized memory. Therefore, a dedicated KMSAN fuzzing session is not required.",
"NeedsKMSAN": false,
"Reasoning": "The patch modifies core MPTCP request socket cloning, token hash management, and socket clone error handling during TCP/MPTCP connection establishment. This logic involves subtle RCU, refcounting, and locking semantics that are fully reachable via socket syscalls in standard virtualized environments.",
"WorthFuzzing": true
} |
| 1/1 | 2026/09/08 21:09 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 4f300fe782771a2a08bfa31d9c5babfcfad0116e\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Tue Sep 8 21:09:53 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/net/mptcp.h b/include/net/mptcp.h\nindex 485d55b66ea67..ad7005b574bb1 100644\n--- a/include/net/mptcp.h\n+++ b/include/net/mptcp.h\n@@ -219,6 +219,9 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,\n struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,\n \t\t\t\t\t struct sock *sk_listener,\n \t\t\t\t\t bool attach_listener);\n+/* Caller must hold an RCU read-side lock. */\n+void mptcp_subflow_reqsk_clone(struct request_sock *req,\n+\t\t\t struct request_sock *new_req);\n \n __be32 mptcp_get_reset_option(const struct sk_buff *skb);\n \n@@ -305,6 +308,12 @@ static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct reques\n \treturn NULL;\n }\n \n+/* Caller must hold an RCU read-side lock. */\n+static inline void mptcp_subflow_reqsk_clone(struct request_sock *req,\n+\t\t\t\t\t struct request_sock *new_req)\n+{\n+}\n+\n static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); }\n \n static inline void mptcp_active_detect_blackhole(struct sock *sk, bool expired) { }\ndiff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c\nindex 6257459bcee24..896f472dcba29 100644\n--- a/net/ipv4/inet_connection_sock.c\n+++ b/net/ipv4/inet_connection_sock.c\n@@ -21,6 +21,7 @@\n #include \u003cnet/xfrm.h\u003e\n #include \u003cnet/tcp.h\u003e\n #include \u003cnet/tcp_ecn.h\u003e\n+#include \u003cnet/mptcp.h\u003e\n #include \u003cnet/sock_reuseport.h\u003e\n #include \u003cnet/addrconf.h\u003e\n \n@@ -961,6 +962,9 @@ static struct request_sock *inet_reqsk_clone(struct request_sock *req,\n \t\trcu_assign_pointer(tcp_sk(nreq-\u003esk)-\u003efastopen_rsk, nreq);\n \t}\n \n+\tif (rsk_is_mptcp(req))\n+\t\tmptcp_subflow_reqsk_clone(req, nreq);\n+\n \treturn nreq;\n }\n \ndiff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c\nindex e1f08f71cdb16..30067f2a7ca8f 100644\n--- a/net/mptcp/protocol.c\n+++ b/net/mptcp/protocol.c\n@@ -3692,6 +3692,24 @@ static void mptcp_copy_ip_options(struct sock *newsk, const struct sock *sk)\n \trcu_read_unlock();\n }\n \n+static void mptcp_sk_clone_destroy(struct sock *nsk)\n+{\n+\tstruct mptcp_sock *msk = mptcp_sk(nsk);\n+\n+\tmptcp_release_sched(msk);\n+\tmptcp_set_state(nsk, TCP_CLOSE);\n+\t/* inet_csk_prepare_forced_close() clears TCP sock_ops state via\n+\t * tcp_sk(), but nsk is an MPTCP master socket; keep the inet-level\n+\t * destroy preparation here.\n+\t */\n+\tbh_unlock_sock(nsk);\n+\tsock_put(nsk);\n+\tsock_set_flag(nsk, SOCK_DEAD);\n+\ttcp_orphan_count_inc();\n+\tinet_sk(nsk)-\u003einet_num = 0;\n+\tinet_csk_destroy_sock(nsk);\n+}\n+\n struct sock *mptcp_sk_clone_init(const struct sock *sk,\n \t\t\t\t const struct mptcp_options_received *mp_opt,\n \t\t\t\t struct sock *ssk,\n@@ -3751,11 +3769,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,\n \tlist_add(\u0026subflow-\u003enode, \u0026msk-\u003econn_list);\n \tsock_hold(ssk);\n \n-\t/* new mpc subflow takes ownership of the newly\n-\t * created mptcp socket\n-\t */\n-\tmptcp_token_accept(subflow_req, msk);\n-\n \t/* set msk addresses early to ensure mptcp_pm_get_local_id()\n \t * uses the correct data\n \t */\n@@ -3764,6 +3777,14 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,\n \tmptcp_rcv_space_init(msk, ssk);\n \tmsk-\u003ercvq_space.time = mptcp_stamp();\n \n+\tif (!mptcp_token_accept(subflow_req, msk)) {\n+\t\tlist_del_init(\u0026subflow-\u003enode);\n+\t\tWRITE_ONCE(msk-\u003efirst, NULL);\n+\t\tsock_put(ssk);\n+\t\tmptcp_sk_clone_destroy(nsk);\n+\t\treturn NULL;\n+\t}\n+\n \tif (mp_opt-\u003esuboptions \u0026 OPTION_MPTCP_MPC_ACK)\n \t\t__mptcp_subflow_fully_established(msk, subflow, mp_opt);\n \tbh_unlock_sock(nsk);\ndiff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h\nindex 87ccb84e9927c..247449cc2feb9 100644\n--- a/net/mptcp/protocol.h\n+++ b/net/mptcp/protocol.h\n@@ -1079,9 +1079,11 @@ static inline void mptcp_token_init_request(struct request_sock *req)\n }\n \n int mptcp_token_new_request(struct request_sock *req);\n+void mptcp_token_move_request(struct request_sock *req,\n+\t\t\t struct request_sock *new_req);\n void mptcp_token_destroy_request(struct request_sock *req);\n int mptcp_token_new_connect(struct sock *ssk);\n-void mptcp_token_accept(struct mptcp_subflow_request_sock *r,\n+bool mptcp_token_accept(struct mptcp_subflow_request_sock *r,\n \t\t\tstruct mptcp_sock *msk);\n bool mptcp_token_exists(u32 token);\n struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);\ndiff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c\nindex af81ad5e699d1..d2cd12fc03421 100644\n--- a/net/mptcp/subflow.c\n+++ b/net/mptcp/subflow.c\n@@ -47,6 +47,41 @@ static void subflow_req_destructor(struct request_sock *req)\n \tmptcp_token_destroy_request(req);\n }\n \n+void mptcp_subflow_reqsk_clone(struct request_sock *req,\n+\t\t\t struct request_sock *new_req)\n+{\n+\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\n+\tstruct mptcp_subflow_request_sock *new_subflow_req;\n+\tstruct mptcp_sock *msk;\n+\n+\tnew_subflow_req = mptcp_subflow_rsk(new_req);\n+\tRCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),\n+\t\t\t \"MPTCP reqsk clone called without RCU\");\n+\n+\t/* A non-NULL -\u003emsk means the request owns one reference. The clone\n+\t * copied only the pointer, while the original request can concurrently\n+\t * transfer its reference to the child. Acquire a reference for the\n+\t * clone, then verify that the original request still owns the same msk.\n+\t * MPTCP sockets use SLAB_TYPESAFE_BY_RCU and all clone callers run in\n+\t * an RCU read-side critical section, keeping the memory stable here.\n+\t */\n+\tmsk = READ_ONCE(subflow_req-\u003emsk);\n+\tif (msk) {\n+\t\tstruct sock *sk = (struct sock *)msk;\n+\n+\t\tif (!refcount_inc_not_zero_acquire(\u0026sk-\u003esk_refcnt)) {\n+\t\t\tmsk = NULL;\n+\t\t} else if (READ_ONCE(subflow_req-\u003emsk) != msk) {\n+\t\t\tsock_put(sk);\n+\t\t\tmsk = NULL;\n+\t\t}\n+\t}\n+\n+\tnew_subflow_req-\u003emsk = msk;\n+\n+\tmptcp_token_move_request(req, new_req);\n+}\n+\n static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,\n \t\t\t\t void *hmac)\n {\n@@ -885,8 +920,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,\n \n \t\tif (ctx-\u003emp_capable) {\n \t\t\tctx-\u003econn = mptcp_sk_clone_init(listener-\u003econn, \u0026mp_opt, child, req);\n-\t\t\tif (!ctx-\u003econn)\n+\t\t\tif (!ctx-\u003econn) {\n+\t\t\t\tfallback = true;\n \t\t\t\tgoto fallback;\n+\t\t\t}\n \n \t\t\tctx-\u003esubflow_id = 1;\n \t\t\towner = mptcp_sk(ctx-\u003econn);\n@@ -923,7 +960,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,\n \t\t\t}\n \n \t\t\t/* move the msk reference ownership to the subflow */\n-\t\t\tsubflow_req-\u003emsk = NULL;\n+\t\t\tWRITE_ONCE(subflow_req-\u003emsk, NULL);\n \t\t\tctx-\u003econn = (struct sock *)owner;\n \n \t\t\tif (subflow_use_different_sport(owner, sk)) {\ndiff --git a/net/mptcp/token.c b/net/mptcp/token.c\nindex f1a50f367add8..e0f2823f92efb 100644\n--- a/net/mptcp/token.c\n+++ b/net/mptcp/token.c\n@@ -180,6 +180,43 @@ int mptcp_token_new_connect(struct sock *ssk)\n \treturn 0;\n }\n \n+/**\n+ * mptcp_token_move_request - move request token ownership to a clone\n+ * @req: original request socket\n+ * @new_req: cloned request socket\n+ *\n+ * Move the token hash entry from the original request to its clone.\n+ */\n+void mptcp_token_move_request(struct request_sock *req,\n+\t\t\t struct request_sock *new_req)\n+{\n+\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\n+\tstruct mptcp_subflow_request_sock *new_subflow_req;\n+\tstruct mptcp_subflow_request_sock *pos;\n+\tstruct token_bucket *bucket;\n+\n+\tnew_subflow_req = mptcp_subflow_rsk(new_req);\n+\n+\tif (hlist_nulls_unhashed_lockless(\u0026subflow_req-\u003etoken_node)) {\n+\t\tmptcp_token_init_request(new_req);\n+\t\treturn;\n+\t}\n+\n+\tbucket = token_bucket(subflow_req-\u003etoken);\n+\tspin_lock_bh(\u0026bucket-\u003elock);\n+\tif (hlist_nulls_unhashed(\u0026subflow_req-\u003etoken_node)) {\n+\t\tmptcp_token_init_request(new_req);\n+\t} else {\n+\t\tpos = __token_lookup_req(bucket, subflow_req-\u003etoken);\n+\t\tif (pos == subflow_req)\n+\t\t\thlist_nulls_replace_init_rcu(\u0026subflow_req-\u003etoken_node,\n+\t\t\t\t\t\t \u0026new_subflow_req-\u003etoken_node);\n+\t\telse\n+\t\t\tmptcp_token_init_request(new_req);\n+\t}\n+\tspin_unlock_bh(\u0026bucket-\u003elock);\n+}\n+\n /**\n * mptcp_token_accept - replace a req sk with full sock in token hash\n * @req: the request socket to be removed\n@@ -187,24 +224,36 @@ int mptcp_token_new_connect(struct sock *ssk)\n *\n * Called when a SYN packet creates a new logical connection, i.e.\n * is not a join request.\n+ *\n+ * Return: true on success.\n */\n-void mptcp_token_accept(struct mptcp_subflow_request_sock *req,\n+bool mptcp_token_accept(struct mptcp_subflow_request_sock *req,\n \t\t\tstruct mptcp_sock *msk)\n {\n \tstruct mptcp_subflow_request_sock *pos;\n \tstruct sock *sk = (struct sock *)msk;\n \tstruct token_bucket *bucket;\n+\tbool ret = false;\n \n-\tsock_prot_inuse_add(sock_net(sk), sk-\u003esk_prot, 1);\n \tbucket = token_bucket(req-\u003etoken);\n \tspin_lock_bh(\u0026bucket-\u003elock);\n+\tif (hlist_nulls_unhashed(\u0026req-\u003etoken_node))\n+\t\tgoto unlock;\n \n-\t/* pedantic lookup check for the moved token */\n \tpos = __token_lookup_req(bucket, req-\u003etoken);\n-\tif (!WARN_ON_ONCE(pos != req))\n-\t\thlist_nulls_del_init_rcu(\u0026req-\u003etoken_node);\n+\tif (pos != req)\n+\t\tgoto unlock;\n+\n+\thlist_nulls_del_init_rcu(\u0026req-\u003etoken_node);\n \t__sk_nulls_add_node_rcu((struct sock *)msk, \u0026bucket-\u003emsk_chain);\n+\tret = true;\n+\n+unlock:\n \tspin_unlock_bh(\u0026bucket-\u003elock);\n+\tif (ret)\n+\t\tsock_prot_inuse_add(sock_net(sk), sk-\u003esk_prot, 1);\n+\n+\treturn ret;\n }\n \n bool mptcp_token_exists(u32 token)\n@@ -355,16 +404,21 @@ void mptcp_token_destroy_request(struct request_sock *req)\n \tstruct mptcp_subflow_request_sock *pos;\n \tstruct token_bucket *bucket;\n \n-\tif (hlist_nulls_unhashed(\u0026subflow_req-\u003etoken_node))\n+\tif (hlist_nulls_unhashed_lockless(\u0026subflow_req-\u003etoken_node))\n \t\treturn;\n \n \tbucket = token_bucket(subflow_req-\u003etoken);\n \tspin_lock_bh(\u0026bucket-\u003elock);\n+\tif (hlist_nulls_unhashed(\u0026subflow_req-\u003etoken_node))\n+\t\tgoto unlock;\n+\n \tpos = __token_lookup_req(bucket, subflow_req-\u003etoken);\n-\tif (!WARN_ON_ONCE(pos != subflow_req)) {\n+\tif (pos == subflow_req) {\n \t\thlist_nulls_del_init_rcu(\u0026pos-\u003etoken_node);\n \t\tbucket-\u003echain_len--;\n \t}\n+\n+unlock:\n \tspin_unlock_bh(\u0026bucket-\u003elock);\n }\n \ndiff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c\nindex 4fc39fa2e262d..be9acce8a5673 100644\n--- a/net/mptcp/token_test.c\n+++ b/net/mptcp/token_test.c\n@@ -99,7 +99,7 @@ static void mptcp_token_test_accept(struct kunit *test)\n \tKUNIT_ASSERT_EQ(test, 0,\n \t\t\tmptcp_token_new_request((struct request_sock *)req));\n \tmsk-\u003etoken = req-\u003etoken;\n-\tmptcp_token_accept(req, msk);\n+\tKUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));\n \tKUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(\u0026init_net, msk-\u003etoken));\n \n \t/* this is now a no-op */\n@@ -122,7 +122,7 @@ static void mptcp_token_test_destroyed(struct kunit *test)\n \tKUNIT_ASSERT_EQ(test, 0,\n \t\t\tmptcp_token_new_request((struct request_sock *)req));\n \tmsk-\u003etoken = req-\u003etoken;\n-\tmptcp_token_accept(req, msk);\n+\tKUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));\n \n \t/* simulate race on removal */\n \trefcount_set(\u0026sk-\u003esk_refcnt, 0);\n"
} |
| 2/1 | 2026/09/08 21:09 | agent | patch-evaluator |
0mModel:core Args: null Results: {
"EnableConfigs": [
"MPTCP"
],
"FocusSymbols": [
"mptcp_subflow_reqsk_clone",
"mptcp_token_move_request",
"mptcp_token_accept",
"mptcp_token_destroy_request",
"mptcp_sk_clone_init",
"subflow_syn_recv_sock",
"inet_reqsk_clone"
],
"Reasoning": "The patch modifies core MPTCP request socket cloning, token hash management, and socket clone error handling during TCP/MPTCP connection establishment. This logic involves subtle RCU, refcounting, and locking semantics that are fully reachable via socket syscalls in standard virtualized environments.",
"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 4f300fe782771a2a08bfa31d9c5babfcfad0116e
Author: syz-cluster <triage@syzkaller.com>
Date: Tue Sep 8 21:09:53 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 485d55b66ea67..ad7005b574bb1 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -219,6 +219,9 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk_listener,
bool attach_listener);
+/* Caller must hold an RCU read-side lock. */
+void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req);
__be32 mptcp_get_reset_option(const struct sk_buff *skb);
@@ -305,6 +308,12 @@ static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct reques
return NULL;
}
+/* Caller must hold an RCU read-side lock. */
+static inline void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req)
+{
+}
+
static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); }
static inline void mptcp_active_detect_blackhole(struct sock *sk, bool expired) { }
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 6257459bcee24..896f472dcba29 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -21,6 +21,7 @@
#include <net/xfrm.h>
#include <net/tcp.h>
#include <net/tcp_ecn.h>
+#include <net/mptcp.h>
#include <net/sock_reuseport.h>
#include <net/addrconf.h>
@@ -961,6 +962,9 @@ static struct request_sock *inet_reqsk_clone(struct request_sock *req,
rcu_assign_pointer(tcp_sk(nreq->sk)->fastopen_rsk, nreq);
}
+ if (rsk_is_mptcp(req))
+ mptcp_subflow_reqsk_clone(req, nreq);
+
return nreq;
}
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e1f08f71cdb16..30067f2a7ca8f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3692,6 +3692,24 @@ static void mptcp_copy_ip_options(struct sock *newsk, const struct sock *sk)
rcu_read_unlock();
}
+static void mptcp_sk_clone_destroy(struct sock *nsk)
+{
+ struct mptcp_sock *msk = mptcp_sk(nsk);
+
+ mptcp_release_sched(msk);
+ mptcp_set_state(nsk, TCP_CLOSE);
+ /* inet_csk_prepare_forced_close() clears TCP sock_ops state via
+ * tcp_sk(), but nsk is an MPTCP master socket; keep the inet-level
+ * destroy preparation here.
+ */
+ bh_unlock_sock(nsk);
+ sock_put(nsk);
+ sock_set_flag(nsk, SOCK_DEAD);
+ tcp_orphan_count_inc();
+ inet_sk(nsk)->inet_num = 0;
+ inet_csk_destroy_sock(nsk);
+}
+
struct sock *mptcp_sk_clone_init(const struct sock *sk,
const struct mptcp_options_received *mp_opt,
struct sock *ssk,
@@ -3751,11 +3769,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
list_add(&subflow->node, &msk->conn_list);
sock_hold(ssk);
- /* new mpc subflow takes ownership of the newly
- * created mptcp socket
- */
- mptcp_token_accept(subflow_req, msk);
-
/* set msk addresses early to ensure mptcp_pm_get_local_id()
* uses the correct data
*/
@@ -3764,6 +3777,14 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
mptcp_rcv_space_init(msk, ssk);
msk->rcvq_space.time = mptcp_stamp();
+ if (!mptcp_token_accept(subflow_req, msk)) {
+ list_del_init(&subflow->node);
+ WRITE_ONCE(msk->first, NULL);
+ sock_put(ssk);
+ mptcp_sk_clone_destroy(nsk);
+ return NULL;
+ }
+
if (mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
__mptcp_subflow_fully_established(msk, subflow, mp_opt);
bh_unlock_sock(nsk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 87ccb84e9927c..247449cc2feb9 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1079,9 +1079,11 @@ static inline void mptcp_token_init_request(struct request_sock *req)
}
int mptcp_token_new_request(struct request_sock *req);
+void mptcp_token_move_request(struct request_sock *req,
+ struct request_sock *new_req);
void mptcp_token_destroy_request(struct request_sock *req);
int mptcp_token_new_connect(struct sock *ssk);
-void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
+bool mptcp_token_accept(struct mptcp_subflow_request_sock *r,
struct mptcp_sock *msk);
bool mptcp_token_exists(u32 token);
struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index af81ad5e699d1..d2cd12fc03421 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -47,6 +47,41 @@ static void subflow_req_destructor(struct request_sock *req)
mptcp_token_destroy_request(req);
}
+void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req)
+{
+ struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+ struct mptcp_subflow_request_sock *new_subflow_req;
+ struct mptcp_sock *msk;
+
+ new_subflow_req = mptcp_subflow_rsk(new_req);
+ RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
+ "MPTCP reqsk clone called without RCU");
+
+ /* A non-NULL ->msk means the request owns one reference. The clone
+ * copied only the pointer, while the original request can concurrently
+ * transfer its reference to the child. Acquire a reference for the
+ * clone, then verify that the original request still owns the same msk.
+ * MPTCP sockets use SLAB_TYPESAFE_BY_RCU and all clone callers run in
+ * an RCU read-side critical section, keeping the memory stable here.
+ */
+ msk = READ_ONCE(subflow_req->msk);
+ if (msk) {
+ struct sock *sk = (struct sock *)msk;
+
+ if (!refcount_inc_not_zero_acquire(&sk->sk_refcnt)) {
+ msk = NULL;
+ } else if (READ_ONCE(subflow_req->msk) != msk) {
+ sock_put(sk);
+ msk = NULL;
+ }
+ }
+
+ new_subflow_req->msk = msk;
+
+ mptcp_token_move_request(req, new_req);
+}
+
static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
void *hmac)
{
@@ -885,8 +920,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
if (ctx->mp_capable) {
ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
- if (!ctx->conn)
+ if (!ctx->conn) {
+ fallback = true;
goto fallback;
+ }
ctx->subflow_id = 1;
owner = mptcp_sk(ctx->conn);
@@ -923,7 +960,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
}
/* move the msk reference ownership to the subflow */
- subflow_req->msk = NULL;
+ WRITE_ONCE(subflow_req->msk, NULL);
ctx->conn = (struct sock *)owner;
if (subflow_use_different_sport(owner, sk)) {
diff --git a/net/mptcp/token.c b/net/mptcp/token.c
index f1a50f367add8..e0f2823f92efb 100644
--- a/net/mptcp/token.c
+++ b/net/mptcp/token.c
@@ -180,6 +180,43 @@ int mptcp_token_new_connect(struct sock *ssk)
return 0;
}
+/**
+ * mptcp_token_move_request - move request token ownership to a clone
+ * @req: original request socket
+ * @new_req: cloned request socket
+ *
+ * Move the token hash entry from the original request to its clone.
+ */
+void mptcp_token_move_request(struct request_sock *req,
+ struct request_sock *new_req)
+{
+ struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+ struct mptcp_subflow_request_sock *new_subflow_req;
+ struct mptcp_subflow_request_sock *pos;
+ struct token_bucket *bucket;
+
+ new_subflow_req = mptcp_subflow_rsk(new_req);
+
+ if (hlist_nulls_unhashed_lockless(&subflow_req->token_node)) {
+ mptcp_token_init_request(new_req);
+ return;
+ }
+
+ bucket = token_bucket(subflow_req->token);
+ spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&subflow_req->token_node)) {
+ mptcp_token_init_request(new_req);
+ } else {
+ pos = __token_lookup_req(bucket, subflow_req->token);
+ if (pos == subflow_req)
+ hlist_nulls_replace_init_rcu(&subflow_req->token_node,
+ &new_subflow_req->token_node);
+ else
+ mptcp_token_init_request(new_req);
+ }
+ spin_unlock_bh(&bucket->lock);
+}
+
/**
* mptcp_token_accept - replace a req sk with full sock in token hash
* @req: the request socket to be removed
@@ -187,24 +224,36 @@ int mptcp_token_new_connect(struct sock *ssk)
*
* Called when a SYN packet creates a new logical connection, i.e.
* is not a join request.
+ *
+ * Return: true on success.
*/
-void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
+bool mptcp_token_accept(struct mptcp_subflow_request_sock *req,
struct mptcp_sock *msk)
{
struct mptcp_subflow_request_sock *pos;
struct sock *sk = (struct sock *)msk;
struct token_bucket *bucket;
+ bool ret = false;
- sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
bucket = token_bucket(req->token);
spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&req->token_node))
+ goto unlock;
- /* pedantic lookup check for the moved token */
pos = __token_lookup_req(bucket, req->token);
- if (!WARN_ON_ONCE(pos != req))
- hlist_nulls_del_init_rcu(&req->token_node);
+ if (pos != req)
+ goto unlock;
+
+ hlist_nulls_del_init_rcu(&req->token_node);
__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+ ret = true;
+
+unlock:
spin_unlock_bh(&bucket->lock);
+ if (ret)
+ sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+
+ return ret;
}
bool mptcp_token_exists(u32 token)
@@ -355,16 +404,21 @@ void mptcp_token_destroy_request(struct request_sock *req)
struct mptcp_subflow_request_sock *pos;
struct token_bucket *bucket;
- if (hlist_nulls_unhashed(&subflow_req->token_node))
+ if (hlist_nulls_unhashed_lockless(&subflow_req->token_node))
return;
bucket = token_bucket(subflow_req->token);
spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&subflow_req->token_node))
+ goto unlock;
+
pos = __token_lookup_req(bucket, subflow_req->token);
- if (!WARN_ON_ONCE(pos != subflow_req)) {
+ if (pos == subflow_req) {
hlist_nulls_del_init_rcu(&pos->token_node);
bucket->chain_len--;
}
+
+unlock:
spin_unlock_bh(&bucket->lock);
}
diff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c
index 4fc39fa2e262d..be9acce8a5673 100644
--- a/net/mptcp/token_test.c
+++ b/net/mptcp/token_test.c
@@ -99,7 +99,7 @@ static void mptcp_token_test_accept(struct kunit *test)
KUNIT_ASSERT_EQ(test, 0,
mptcp_token_new_request((struct request_sock *)req));
msk->token = req->token;
- mptcp_token_accept(req, msk);
+ KUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));
KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
/* this is now a no-op */
@@ -122,7 +122,7 @@ static void mptcp_token_test_destroyed(struct kunit *test)
KUNIT_ASSERT_EQ(test, 0,
mptcp_token_new_request((struct request_sock *)req));
msk->token = req->token;
- mptcp_token_accept(req, msk);
+ KUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));
/* simulate race on removal */
refcount_set(&sk->sk_refcnt, 0);
|
| 3/2 | 2026/09/08 21:09 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 7174 output: 29 thoughts: 431 Thoughts: **Analyzing the Patch for Fuzzing Potential** Okay, let's break this patch down and figure out if it's fuzzable, what configurations we'll need, and which symbols are the most promising targets. My initial thought is to dive into the patch details. First, I see the following files are touched: `include/net/mptcp.h`, `net/ipv4/inet_connection_sock.c`, `net/mptcp/protocol.c`, `net/mptcp/protocol.h`, `net/mptcp/subflow.c`, `net/mptcp/token.c`, and `net/mptcp/token_test.c`. The changes seem to center around `mptcp_subflow_reqsk_clone`, `mptcp_sk_clone_init` and token handling within the MPTCP stack, potentially implementing and refining the subflow cloning process. Now, the important question: Is this *reachable* code? Absolutely. MPTCP is part of the core Linux networking stack. It's accessible via standard socket syscalls and, thankfully, can be exercised with network traffic, loopback, tun/tap interfaces, and QEMU or a cloud environment. That’s a big win for fuzzing. Next, I need to check the Kconfig dependencies for MPTCP. I'll fire up `grepper` or just quickly check the `net/mptcp/Kconfig` file. This is crucial to ensure that MPTCP is enabled in a config before I try to target it with my fuzzing setup. Gotta make sure it's even compiled in! |
| 4/2 | 2026/09/08 21:09 | tool | grepper |
0mArgs:{
"Expression": "config MPTCP",
"PathPrefix": "net/mptcp"
}Results: {
"Output": "net/mptcp/Kconfig-1-\nnet/mptcp/Kconfig:2:config MPTCP\nnet/mptcp/Kconfig-3-\tbool \"MPTCP: Multipath TCP\"\n--\nnet/mptcp/Kconfig=16=config INET_MPTCP_DIAG\n--\nnet/mptcp/Kconfig-19-\nnet/mptcp/Kconfig:20:config MPTCP_IPV6\nnet/mptcp/Kconfig-21-\tbool \"MPTCP: IPv6 support for Multipath TCP\"\n--\nnet/mptcp/Kconfig-24-\nnet/mptcp/Kconfig:25:config MPTCP_KUNIT_TEST\nnet/mptcp/Kconfig-26-\ttristate \"This builds the MPTCP KUnit tests\" if !KUNIT_ALL_TESTS\n"
} |
| 5/2 | 2026/09/08 21:09 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8212 output: 34 thoughts: 22 Thoughts: Here's my summary, as though I'm reading and processing the `net/mptcp/Kconfig` file: **Analyzing the MPTCP Configuration Options** Okay, let's dive into this `net/mptcp/Kconfig` file, specifically the initial lines, say the first thirty or so. I need to get a handle on the basic configuration options for Multipath TCP. This is where the kernel's build system defines what features are available, how they're enabled, and any dependencies. I expect to see the core MPTCP module defined first, likely with a `CONFIG_MPTCP` symbol. Then, I'll be looking for flags that control specific features – maybe support for different subflow schedulers, or the inclusion of particular congestion control algorithms. I'll be keeping an eye out for any dependencies on other kernel subsystems, like TCP or NET. I'm also anticipating some `help` text that describes what each option does. It's crucial to understand these flags thoroughly since they directly influence how MPTCP behaves in different scenarios. I'm interested in the defaults, too. They will give a hint as to what the developers thought would be the common and useful configuration options. I'm especially interested in whether any experimental or potentially unstable features are enabled or disabled by default. Okay, let's start reading... |
| 6/2 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/mptcp/Kconfig",
"FirstLine": 1,
"LineCount": 35
}Results: {
"Contents": " 1:\t\n 2:\tconfig MPTCP\n 3:\t\tbool \"MPTCP: Multipath TCP\"\n 4:\t\tdepends on INET\n 5:\t\tselect SKB_EXTENSIONS\n 6:\t\tselect CRYPTO_LIB_SHA256\n 7:\t\tselect CRYPTO_LIB_UTILS\n 8:\t\thelp\n 9:\t\t Multipath TCP (MPTCP) connections send and receive data over multiple\n 10:\t\t subflows in order to utilize multiple network paths. Each subflow\n 11:\t\t uses the TCP protocol, and TCP options carry header information for\n 12:\t\t MPTCP.\n 13:\t\n 14:\tif MPTCP\n 15:\t\n 16:\tconfig INET_MPTCP_DIAG\n 17:\t\tdepends on INET_DIAG\n 18:\t\tdef_tristate INET_DIAG\n 19:\t\n 20:\tconfig MPTCP_IPV6\n 21:\t\tbool \"MPTCP: IPv6 support for Multipath TCP\"\n 22:\t\tdepends on IPV6=y\n 23:\t\tdefault y\n 24:\t\n 25:\tconfig MPTCP_KUNIT_TEST\n 26:\t\ttristate \"This builds the MPTCP KUnit tests\" if !KUNIT_ALL_TESTS\n 27:\t\tdepends on KUNIT\n 28:\t\tdefault KUNIT_ALL_TESTS\n 29:\t\thelp\n 30:\t\t Currently covers the MPTCP crypto and token helpers.\n 31:\t\t Only useful for kernel devs running KUnit test harness and are not\n 32:\t\t for inclusion into a production build.\n 33:\t\n 34:\t\t For more information on KUnit and unit tests in general please refer\n 35:\t\t to the KUnit documentation in Documentation/dev-tools/kunit/.\n"
} |
| 7/2 | 2026/09/08 21:10 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9023 output: 20 thoughts: 21 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: **Analyzing the Triggering Mechanisms of `inet_reqsk_clone`** Okay, so I need to understand the contexts in which `inet_reqsk_clone` is invoked. It's a critical function, so knowing its call paths is essential for understanding connection establishment and potential race conditions in the TCP/IP stack. Time to dig into the code and trace the calls. I'll start with a straightforward search for its direct callers to map out the initial set of possibilities. This will give me the entry points, and from there, I'll probably need to understand the logic that leads to those calls. Depending on the architecture, I might need to consider compiler optimizations or inlining that could obfuscate the call graph somewhat, but the basics should be discernible. I'm especially interested in looking at the arguments being passed to it, to see the kind of information that it is working with. Understanding that data flow is often key. |
| 8/2 | 2026/09/08 21:10 | tool | grepper |
0mArgs:{
"Expression": "inet_reqsk_clone"
}Results: {
"Output": "net/ipv4/inet_connection_sock.c=905=void __reqsk_free(struct request_sock *req)\n--\nnet/ipv4/inet_connection_sock.c-913-\nnet/ipv4/inet_connection_sock.c:914:static struct request_sock *inet_reqsk_clone(struct request_sock *req,\nnet/ipv4/inet_connection_sock.c-915-\t\t\t\t\t struct sock *sk)\n--\nnet/ipv4/inet_connection_sock.c=1037=static void reqsk_timer_handler(struct timer_list *t)\n--\nnet/ipv4/inet_connection_sock.c-1053-\nnet/ipv4/inet_connection_sock.c:1054:\t\tnreq = inet_reqsk_clone(req, nsk);\nnet/ipv4/inet_connection_sock.c-1055-\t\tif (!nreq)\n--\nnet/ipv4/inet_connection_sock.c=1421=struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,\n--\nnet/ipv4/inet_connection_sock.c-1434-\t\t\t/* hold a refcnt for the nreq-\u003ersk_listener\nnet/ipv4/inet_connection_sock.c:1435:\t\t\t * which is assigned in inet_reqsk_clone()\nnet/ipv4/inet_connection_sock.c-1436-\t\t\t */\nnet/ipv4/inet_connection_sock.c-1437-\t\t\tsock_hold(sk);\nnet/ipv4/inet_connection_sock.c:1438:\t\t\tnreq = inet_reqsk_clone(req, sk);\nnet/ipv4/inet_connection_sock.c-1439-\t\t\tif (!nreq) {\n--\nnet/ipv4/inet_connection_sock.c=1470=void inet_csk_listen_stop(struct sock *sk)\n--\nnet/ipv4/inet_connection_sock.c-1494-\t\tif (nsk) {\nnet/ipv4/inet_connection_sock.c:1495:\t\t\tnreq = inet_reqsk_clone(req, nsk);\nnet/ipv4/inet_connection_sock.c-1496-\t\t\tif (nreq) {\n"
} |
| 9/2 | 2026/09/08 21:10 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9864 output: 27 thoughts: 724 Thoughts: **MPTCP Request Socket Cloning: A Deep Dive** Okay, so I'm looking at this code and immediately see a central theme: cloning request sockets, particularly within the context of MPTCP. `inet_reqsk_clone` is the base function, used in standard TCP listener scenarios, and reuseport, and SYN-ACK retransmissions, fastopen, listen stop situations, handling migrations and cloning of request sockets in various contexts, including timers. However, the interesting part is the MPTCP-specific functions. I see `mptcp_subflow_reqsk_clone`, which handles the MPTCP-specific cloning, dealing with references and token movements. I've also got my eye on `mptcp_token_move_request`, `mptcp_token_accept`, `mptcp_sk_clone_init`, and `mptcp_sk_clone_destroy`. Also note `subflow_syn_recv_sock` is in the mix here. It looks like these functions are the key modifications, all dealing with cloning or token management. Now, let me check the specific functions of interest. I've got `mptcp_subflow_reqsk_clone`, `mptcp_token_move_request`, `mptcp_token_accept`, `mptcp_sk_clone_init`, and `subflow_syn_recv_sock`. I've also noted that `inet_reqsk_clone` is in the list, but it's more general and not MPTCP-specific. `inet_reqsk_clone` is used in multiple places, `reqsk_timer_handler`, `inet_csk_complete_hashdance`, and `inet_csk_listen_stop` in TCP connection handling. That's a good indication of its ubiquity and therefore not a good focus for fuzzing. However, those MPTCP specific functions really look like good targets. Okay, let's assess if this area is "WorthFuzzing". Definitely. It ticks all the boxes. We're talking core networking, fundamental protocol changes. We have complex concurrency concerns - RCU, refcounts, locking, token table manipulation, and cloning under reuseport or syn-ack timers... this screams potential bugs. And yes, it's all reachable through standard socket syscalls within QEMU with loopback or a virtual network. So this is a clear "yes". Finally, what are the relevant configurations? `MPTCP` is the big one. It's a fundamental requirement. And of course, `INET` is a dependency. I'll need to check the `net/mptcp/Makefile` to confirm if there are any other key configuration options, but those seem to be the primary ones to be aware of. |
| 10/2 | 2026/09/08 21:10 | tool | grepper |
0mArgs:{
"Expression": "obj-",
"PathPrefix": "net/mptcp"
}Results: {
"Output": "net/mptcp/Makefile-1-# SPDX-License-Identifier: GPL-2.0\nnet/mptcp/Makefile:2:obj-$(CONFIG_MPTCP) += mptcp.o\nnet/mptcp/Makefile-3-\nnet/mptcp/Makefile=4=mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o \\\n--\nnet/mptcp/Makefile-7-\nnet/mptcp/Makefile:8:obj-$(CONFIG_SYN_COOKIES) += syncookies.o\nnet/mptcp/Makefile:9:obj-$(CONFIG_INET_MPTCP_DIAG) += mptcp_diag.o\nnet/mptcp/Makefile-10-\n--\nnet/mptcp/Makefile=12=mptcp_token_test-objs := token_test.o\nnet/mptcp/Makefile:13:obj-$(CONFIG_MPTCP_KUNIT_TEST) += mptcp_crypto_test.o mptcp_token_test.o\nnet/mptcp/Makefile-14-\nnet/mptcp/Makefile:15:obj-$(CONFIG_BPF_SYSCALL) += bpf.o\n"
} |
| 11/2 | 2026/09/08 21:10 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 11525 output: 169 thoughts: 389 Thoughts: **My Assessment of the MPTCP Modification's Fuzzing Potential** Okay, let's break this down. First, I see the build system is correctly configured to include the MPTCP object files (`mptcp.o`, `protocol.o`, `subflow.o`, `token.o`) when `CONFIG_MPTCP` is enabled. That's a good start. Now, let's verify my initial assessment of the kernel symbols that are modified. I confirmed `mptcp_subflow_reqsk_clone`, `mptcp_token_move_request`, `mptcp_token_accept`, `mptcp_sk_clone_init`, `subflow_syn_recv_sock`, and `inet_reqsk_clone` are directly impacted. And additionally, `mptcp_token_destroy_request` and the static `mptcp_sk_clone_destroy` are also relevant. These functions all play a role in MPTCP connection setup and teardown, particularly related to request sockets and tokens. Excellent. So, given this, let's validate that the set-results criteria are met: * **WorthFuzzing**: Yes, absolutely. This patch touches MPTCP request socket cloning logic, token table management, and socket initialization error handling across TCP/MPTCP connection setup paths. Think reuseport migrations and timer handlers – these things have complex RCU, reference count, and locking interactions. It's prime territory for fuzzing. * **Reasoning**: I need to concisely document the rationale. I'll write: "The patch modifies MPTCP request socket cloning logic, token table management, and socket initialization error handling across TCP/MPTCP connection setup paths (e.g. during reuseport migration or timer handlers), which involves complex RCU/refcount/locking state that is fully reachable in standard virtualized environments." * **EnableConfigs**: We clearly need `MPTCP` enabled. However, to ensure that the required core TCP functionality is also enabled, I'll recommend `["INET", "MPTCP"]`. * **FocusSymbols**: The symbols I've identified: `["mptcp_subflow_reqsk_clone", "mptcp_token_move_request", "mptcp_token_accept", "mptcp_token_destroy_request", "mptcp_sk_clone_init", "subflow_syn_recv_sock", "inet_reqsk_clone"]`. I'm confident in this analysis. Let's call `set-results`. I expect this to be a fruitful area for fuzzing. |
| 12/2 | 2026/09/08 21:10 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"MPTCP"
],
"FocusSymbols": [
"mptcp_subflow_reqsk_clone",
"mptcp_token_move_request",
"mptcp_token_accept",
"mptcp_token_destroy_request",
"mptcp_sk_clone_init",
"subflow_syn_recv_sock",
"inet_reqsk_clone"
],
"Reasoning": "The patch modifies core MPTCP request socket cloning, token hash management, and socket clone error handling during TCP/MPTCP connection establishment. This logic involves subtle RCU, refcounting, and locking semantics that are fully reachable via socket syscalls in standard virtualized environments.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"MPTCP"
],
"FocusSymbols": [
"mptcp_subflow_reqsk_clone",
"mptcp_token_move_request",
"mptcp_token_accept",
"mptcp_token_destroy_request",
"mptcp_sk_clone_init",
"subflow_syn_recv_sock",
"inet_reqsk_clone"
],
"Reasoning": "The patch modifies core MPTCP request socket cloning, token hash management, and socket clone error handling during TCP/MPTCP connection establishment. This logic involves subtle RCU, refcounting, and locking semantics that are fully reachable via socket syscalls in standard virtualized environments.",
"WorthFuzzing": true
} |
| 13/1 | 2026/09/08 21:10 | action | If |
0mArgs:{
"WorthFuzzing": true
}Results: null |
| 14/2 | 2026/09/08 21:10 | agent | kmsan-evaluator |
0mModel:core Args: null Results: {
"KMSANReasoning": "The patch fixes MPTCP request socket cloning during reuseport socket migration by safely handling msk socket refcounts, moving token hash table entries (mptcp_token_move_request), and properly cleaning up and falling back when mptcp_token_accept fails.\n\nThese changes involve concurrency, RCU safety, socket refcounting, and lifecycle/destruction state management. Any potential bugs in this area are use-after-free, refcounting issues, or locking/deadlock bugs, which are detected by KASAN, LOCKDEP, and standard kernel sanitizers. The patch does not introduce or modify uninitialized stack/heap allocations, memory copying to userspace, padding/info-leaks, or branching on uninitialized memory. Therefore, a dedicated KMSAN fuzzing session is not required.",
"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 4f300fe782771a2a08bfa31d9c5babfcfad0116e
Author: syz-cluster <triage@syzkaller.com>
Date: Tue Sep 8 21:09:53 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 485d55b66ea67..ad7005b574bb1 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -219,6 +219,9 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk_listener,
bool attach_listener);
+/* Caller must hold an RCU read-side lock. */
+void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req);
__be32 mptcp_get_reset_option(const struct sk_buff *skb);
@@ -305,6 +308,12 @@ static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct reques
return NULL;
}
+/* Caller must hold an RCU read-side lock. */
+static inline void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req)
+{
+}
+
static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); }
static inline void mptcp_active_detect_blackhole(struct sock *sk, bool expired) { }
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 6257459bcee24..896f472dcba29 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -21,6 +21,7 @@
#include <net/xfrm.h>
#include <net/tcp.h>
#include <net/tcp_ecn.h>
+#include <net/mptcp.h>
#include <net/sock_reuseport.h>
#include <net/addrconf.h>
@@ -961,6 +962,9 @@ static struct request_sock *inet_reqsk_clone(struct request_sock *req,
rcu_assign_pointer(tcp_sk(nreq->sk)->fastopen_rsk, nreq);
}
+ if (rsk_is_mptcp(req))
+ mptcp_subflow_reqsk_clone(req, nreq);
+
return nreq;
}
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e1f08f71cdb16..30067f2a7ca8f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3692,6 +3692,24 @@ static void mptcp_copy_ip_options(struct sock *newsk, const struct sock *sk)
rcu_read_unlock();
}
+static void mptcp_sk_clone_destroy(struct sock *nsk)
+{
+ struct mptcp_sock *msk = mptcp_sk(nsk);
+
+ mptcp_release_sched(msk);
+ mptcp_set_state(nsk, TCP_CLOSE);
+ /* inet_csk_prepare_forced_close() clears TCP sock_ops state via
+ * tcp_sk(), but nsk is an MPTCP master socket; keep the inet-level
+ * destroy preparation here.
+ */
+ bh_unlock_sock(nsk);
+ sock_put(nsk);
+ sock_set_flag(nsk, SOCK_DEAD);
+ tcp_orphan_count_inc();
+ inet_sk(nsk)->inet_num = 0;
+ inet_csk_destroy_sock(nsk);
+}
+
struct sock *mptcp_sk_clone_init(const struct sock *sk,
const struct mptcp_options_received *mp_opt,
struct sock *ssk,
@@ -3751,11 +3769,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
list_add(&subflow->node, &msk->conn_list);
sock_hold(ssk);
- /* new mpc subflow takes ownership of the newly
- * created mptcp socket
- */
- mptcp_token_accept(subflow_req, msk);
-
/* set msk addresses early to ensure mptcp_pm_get_local_id()
* uses the correct data
*/
@@ -3764,6 +3777,14 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
mptcp_rcv_space_init(msk, ssk);
msk->rcvq_space.time = mptcp_stamp();
+ if (!mptcp_token_accept(subflow_req, msk)) {
+ list_del_init(&subflow->node);
+ WRITE_ONCE(msk->first, NULL);
+ sock_put(ssk);
+ mptcp_sk_clone_destroy(nsk);
+ return NULL;
+ }
+
if (mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
__mptcp_subflow_fully_established(msk, subflow, mp_opt);
bh_unlock_sock(nsk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 87ccb84e9927c..247449cc2feb9 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1079,9 +1079,11 @@ static inline void mptcp_token_init_request(struct request_sock *req)
}
int mptcp_token_new_request(struct request_sock *req);
+void mptcp_token_move_request(struct request_sock *req,
+ struct request_sock *new_req);
void mptcp_token_destroy_request(struct request_sock *req);
int mptcp_token_new_connect(struct sock *ssk);
-void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
+bool mptcp_token_accept(struct mptcp_subflow_request_sock *r,
struct mptcp_sock *msk);
bool mptcp_token_exists(u32 token);
struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index af81ad5e699d1..d2cd12fc03421 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -47,6 +47,41 @@ static void subflow_req_destructor(struct request_sock *req)
mptcp_token_destroy_request(req);
}
+void mptcp_subflow_reqsk_clone(struct request_sock *req,
+ struct request_sock *new_req)
+{
+ struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+ struct mptcp_subflow_request_sock *new_subflow_req;
+ struct mptcp_sock *msk;
+
+ new_subflow_req = mptcp_subflow_rsk(new_req);
+ RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
+ "MPTCP reqsk clone called without RCU");
+
+ /* A non-NULL ->msk means the request owns one reference. The clone
+ * copied only the pointer, while the original request can concurrently
+ * transfer its reference to the child. Acquire a reference for the
+ * clone, then verify that the original request still owns the same msk.
+ * MPTCP sockets use SLAB_TYPESAFE_BY_RCU and all clone callers run in
+ * an RCU read-side critical section, keeping the memory stable here.
+ */
+ msk = READ_ONCE(subflow_req->msk);
+ if (msk) {
+ struct sock *sk = (struct sock *)msk;
+
+ if (!refcount_inc_not_zero_acquire(&sk->sk_refcnt)) {
+ msk = NULL;
+ } else if (READ_ONCE(subflow_req->msk) != msk) {
+ sock_put(sk);
+ msk = NULL;
+ }
+ }
+
+ new_subflow_req->msk = msk;
+
+ mptcp_token_move_request(req, new_req);
+}
+
static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
void *hmac)
{
@@ -885,8 +920,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
if (ctx->mp_capable) {
ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
- if (!ctx->conn)
+ if (!ctx->conn) {
+ fallback = true;
goto fallback;
+ }
ctx->subflow_id = 1;
owner = mptcp_sk(ctx->conn);
@@ -923,7 +960,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
}
/* move the msk reference ownership to the subflow */
- subflow_req->msk = NULL;
+ WRITE_ONCE(subflow_req->msk, NULL);
ctx->conn = (struct sock *)owner;
if (subflow_use_different_sport(owner, sk)) {
diff --git a/net/mptcp/token.c b/net/mptcp/token.c
index f1a50f367add8..e0f2823f92efb 100644
--- a/net/mptcp/token.c
+++ b/net/mptcp/token.c
@@ -180,6 +180,43 @@ int mptcp_token_new_connect(struct sock *ssk)
return 0;
}
+/**
+ * mptcp_token_move_request - move request token ownership to a clone
+ * @req: original request socket
+ * @new_req: cloned request socket
+ *
+ * Move the token hash entry from the original request to its clone.
+ */
+void mptcp_token_move_request(struct request_sock *req,
+ struct request_sock *new_req)
+{
+ struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+ struct mptcp_subflow_request_sock *new_subflow_req;
+ struct mptcp_subflow_request_sock *pos;
+ struct token_bucket *bucket;
+
+ new_subflow_req = mptcp_subflow_rsk(new_req);
+
+ if (hlist_nulls_unhashed_lockless(&subflow_req->token_node)) {
+ mptcp_token_init_request(new_req);
+ return;
+ }
+
+ bucket = token_bucket(subflow_req->token);
+ spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&subflow_req->token_node)) {
+ mptcp_token_init_request(new_req);
+ } else {
+ pos = __token_lookup_req(bucket, subflow_req->token);
+ if (pos == subflow_req)
+ hlist_nulls_replace_init_rcu(&subflow_req->token_node,
+ &new_subflow_req->token_node);
+ else
+ mptcp_token_init_request(new_req);
+ }
+ spin_unlock_bh(&bucket->lock);
+}
+
/**
* mptcp_token_accept - replace a req sk with full sock in token hash
* @req: the request socket to be removed
@@ -187,24 +224,36 @@ int mptcp_token_new_connect(struct sock *ssk)
*
* Called when a SYN packet creates a new logical connection, i.e.
* is not a join request.
+ *
+ * Return: true on success.
*/
-void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
+bool mptcp_token_accept(struct mptcp_subflow_request_sock *req,
struct mptcp_sock *msk)
{
struct mptcp_subflow_request_sock *pos;
struct sock *sk = (struct sock *)msk;
struct token_bucket *bucket;
+ bool ret = false;
- sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
bucket = token_bucket(req->token);
spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&req->token_node))
+ goto unlock;
- /* pedantic lookup check for the moved token */
pos = __token_lookup_req(bucket, req->token);
- if (!WARN_ON_ONCE(pos != req))
- hlist_nulls_del_init_rcu(&req->token_node);
+ if (pos != req)
+ goto unlock;
+
+ hlist_nulls_del_init_rcu(&req->token_node);
__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+ ret = true;
+
+unlock:
spin_unlock_bh(&bucket->lock);
+ if (ret)
+ sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+
+ return ret;
}
bool mptcp_token_exists(u32 token)
@@ -355,16 +404,21 @@ void mptcp_token_destroy_request(struct request_sock *req)
struct mptcp_subflow_request_sock *pos;
struct token_bucket *bucket;
- if (hlist_nulls_unhashed(&subflow_req->token_node))
+ if (hlist_nulls_unhashed_lockless(&subflow_req->token_node))
return;
bucket = token_bucket(subflow_req->token);
spin_lock_bh(&bucket->lock);
+ if (hlist_nulls_unhashed(&subflow_req->token_node))
+ goto unlock;
+
pos = __token_lookup_req(bucket, subflow_req->token);
- if (!WARN_ON_ONCE(pos != subflow_req)) {
+ if (pos == subflow_req) {
hlist_nulls_del_init_rcu(&pos->token_node);
bucket->chain_len--;
}
+
+unlock:
spin_unlock_bh(&bucket->lock);
}
diff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c
index 4fc39fa2e262d..be9acce8a5673 100644
--- a/net/mptcp/token_test.c
+++ b/net/mptcp/token_test.c
@@ -99,7 +99,7 @@ static void mptcp_token_test_accept(struct kunit *test)
KUNIT_ASSERT_EQ(test, 0,
mptcp_token_new_request((struct request_sock *)req));
msk->token = req->token;
- mptcp_token_accept(req, msk);
+ KUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));
KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
/* this is now a no-op */
@@ -122,7 +122,7 @@ static void mptcp_token_test_destroyed(struct kunit *test)
KUNIT_ASSERT_EQ(test, 0,
mptcp_token_new_request((struct request_sock *)req));
msk->token = req->token;
- mptcp_token_accept(req, msk);
+ KUNIT_EXPECT_TRUE(test, mptcp_token_accept(req, msk));
/* simulate race on removal */
refcount_set(&sk->sk_refcnt, 0);
|
| 15/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 6386 output: 40 thoughts: 691 Thoughts: **Analyzing the Patch Series for KMSAN Fuzzing Needs** Okay, so the task at hand is to determine if this patch series necessitates a dedicated KMSAN fuzzing session. Let's dig in and see what's going on. First, I need to understand what these changes are actually doing. I'm seeing a series of changes related to MPTCP, specifically around request socket cloning and token management. My initial impression is that this is likely a refactoring or improvement related to concurrency and error handling within the MPTCP connection establishment flow. Here’s the breakdown as I understand it: * **Header and Stub:** We have a new stub function `mptcp_subflow_reqsk_clone()` being added to `include/net/mptcp.h`. This suggests some new functionality related to MPTCP subflow cloning. * **Integration with `inet_reqsk_clone()`:** The `inet_connection_sock.c` file now calls this new function `mptcp_subflow_reqsk_clone()` within `inet_reqsk_clone()`. This confirms that the patch is directly related to how MPTCP connections are handled at the lower level inet layer. * **Helper Functions and Error Handling:** `net/mptcp/protocol.c` sees the addition of a destruction helper `mptcp_sk_clone_destroy()` and moves the call to `mptcp_token_accept()`. Critically, `mptcp_token_accept`'s return value is now being *checked* for success. If it fails, the code path now cleans up more gracefully. This implies a significant improvement in the robustness of the token handling process. * **Return Value of `mptcp_token_accept()`:** The return type of `mptcp_token_accept()` is being changed to a boolean. This is a very clear signal that the function can now fail and that this failure is intended to be handled, which confirms my earlier hypothesis. * **`mptcp_subflow_reqsk_clone()` Implementation:** In `net/mptcp/subflow.c`, the new function is implemented. It clones the MPTCP master socket (`msk`) safely using RCU and calls `mptcp_token_move_request()`. This is core logic that I need to understand thoroughly. It also introduces some more robust error handling around failure to initialize a clone. They are using `WRITE_ONCE` to update some `msk` pointers, which points to concurrency and data races. * **Token Handling and Concurrency:** `net/mptcp/token.c` contains the actual implementation of `mptcp_token_move_request()` and updates to `mptcp_token_accept()`, particularly a minor concurrency fix in `mptcp_token_destroy_request()`. This signals that the changes include thread safety improvements to the token replacement. * **Unit Tests:** Finally, `net/mptcp/token_test.c` is updated to reflect the change in `mptcp_token_accept()`'s return value. This is good to see; this signals that they were thinking about how to test the new behavior. Now, I'm especially interested in `inet_reqsk_clone` to see where all of this fits in the bigger picture. I'll read the code or use `grepper` to examine the file and confirm my understanding of the interactions between the different components. Based on this first pass, the changes *appear* to be focused on improving the robustness of the connection establishment process, particularly around concurrency and token management. It's not immediately obvious that this introduces *new* avenues for KMSAN to find issues. However, the changes to error handling, and specifically the use of RCU and `WRITE_ONCE` suggest these changes *could* have introduced subtle data races or concurrency bugs that may be detectable by KMSAN. I would need to analyze the specific code, and potentially use the code browsing tools, to determine the level of concurrency risks. |
| 16/3 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/ipv4/inet_connection_sock.c",
"FirstLine": 945,
"LineCount": 40
}Results: {
"Contents": " 945:\t\tnreq-\u003ersk_listener = sk;\n 946:\t\n 947:\t\tif (sk-\u003esk_protocol == IPPROTO_TCP \u0026\u0026 tcp_rsk(nreq)-\u003etfo_listener) {\n 948:\t\t\tstruct fastopen_queue *fastopenq;\n 949:\t\n 950:\t\t\t/* reqsk_fastopen_remove() will uncharge nreq-\u003ersk_listener,\n 951:\t\t\t * that is @sk, so charge it here. Unlike the listener\n 952:\t\t\t * being closed, @sk is live and needs its lock.\n 953:\t\t\t */\n 954:\t\t\tfastopenq = \u0026inet_csk(sk)-\u003eicsk_accept_queue.fastopenq;\n 955:\t\t\tspin_lock_bh(\u0026fastopenq-\u003elock);\n 956:\t\t\tfastopenq-\u003eqlen++;\n 957:\t\t\tspin_unlock_bh(\u0026fastopenq-\u003elock);\n 958:\t\n 959:\t\t\t/* We need not acquire fastopenq-\u003elock\n 960:\t\t\t * because the child socket is locked in inet_csk_listen_stop().\n 961:\t\t\t */\n 962:\t\t\trcu_assign_pointer(tcp_sk(nreq-\u003esk)-\u003efastopen_rsk, nreq);\n 963:\t\t}\n 964:\t\n 965:\t\tif (rsk_is_mptcp(req))\n 966:\t\t\tmptcp_subflow_reqsk_clone(req, nreq);\n 967:\t\n 968:\t\treturn nreq;\n 969:\t}\n 970:\t\n 971:\tstatic void reqsk_queue_migrated(struct request_sock_queue *queue,\n 972:\t\t\t\t\t const struct request_sock *req)\n 973:\t{\n 974:\t\tif (req-\u003enum_timeout == 0)\n 975:\t\t\tatomic_inc(\u0026queue-\u003eyoung);\n 976:\t\tatomic_inc(\u0026queue-\u003eqlen);\n 977:\t}\n 978:\t\n 979:\tstatic void reqsk_migrate_reset(struct request_sock *req)\n 980:\t{\n 981:\t\treq-\u003esaved_syn = NULL;\n 982:\t#if IS_ENABLED(CONFIG_IPV6)\n 983:\t\tinet_rsk(req)-\u003eipv6_opt = NULL;\n 984:\t\tinet_rsk(req)-\u003epktopts = NULL;\n"
} |
| 17/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8640 output: 40 thoughts: 15 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: **Diving Deeper into inet_reqsk_clone** Alright, so we're looking at the remaining code within `inet_reqsk_clone`. Hmm, seems like we're past the initial setup and error checking. I'm guessing we're now into the meat of it: the actual duplication of the request socket structure for a new connection. I expect to see the resource allocation and data copying. Let's see how they handle potential failure along the way, I'm especially interested in how they maintain consistency if something goes wrong. Considering the complexities of TCP state management, that's always a critical area. I hope it is all done in a consistent manner, as it has to handle the concurrent access. This is going to involve understanding how they deal with the `reqsk` data structure and all the pointers within. What nuances are at play? And how does it relate to the child? It is very important to get this right, and a lot hinges on the right locks. Curious to see the techniques used for atomic operations and memory barriers, particularly if they're dealing with multiple CPUs. Let's see how they've handled that. Okay, I'm ready. Let's dig in. |
| 18/3 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/ipv4/inet_connection_sock.c",
"FirstLine": 920,
"LineCount": 35
}Results: {
"Contents": " 920:\t\tnreq = kmem_cache_alloc(req-\u003ersk_ops-\u003eslab, GFP_ATOMIC | __GFP_NOWARN);\n 921:\t\tif (!nreq) {\n 922:\t\t\t__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);\n 923:\t\n 924:\t\t\t/* paired with refcount_inc_not_zero() in reuseport_migrate_sock() */\n 925:\t\t\tsock_put(sk);\n 926:\t\t\treturn NULL;\n 927:\t\t}\n 928:\t\n 929:\t\treq_sk = req_to_sk(req);\n 930:\t\tnreq_sk = req_to_sk(nreq);\n 931:\t\n 932:\t\tmemcpy(nreq_sk, req_sk,\n 933:\t\t offsetof(struct sock, sk_dontcopy_begin));\n 934:\t\tunsafe_memcpy(\u0026nreq_sk-\u003esk_dontcopy_end, \u0026req_sk-\u003esk_dontcopy_end,\n 935:\t\t\t req-\u003ersk_ops-\u003eobj_size - offsetof(struct sock, sk_dontcopy_end),\n 936:\t\t\t /* alloc is larger than struct, see above */);\n 937:\t\n 938:\t\tsk_node_init(\u0026nreq_sk-\u003esk_node);\n 939:\t\tnreq_sk-\u003esk_tx_queue_mapping = req_sk-\u003esk_tx_queue_mapping;\n 940:\t#ifdef CONFIG_SOCK_RX_QUEUE_MAPPING\n 941:\t\tnreq_sk-\u003esk_rx_queue_mapping = req_sk-\u003esk_rx_queue_mapping;\n 942:\t#endif\n 943:\t\tnreq_sk-\u003esk_incoming_cpu = req_sk-\u003esk_incoming_cpu;\n 944:\t\n 945:\t\tnreq-\u003ersk_listener = sk;\n 946:\t\n 947:\t\tif (sk-\u003esk_protocol == IPPROTO_TCP \u0026\u0026 tcp_rsk(nreq)-\u003etfo_listener) {\n 948:\t\t\tstruct fastopen_queue *fastopenq;\n 949:\t\n 950:\t\t\t/* reqsk_fastopen_remove() will uncharge nreq-\u003ersk_listener,\n 951:\t\t\t * that is @sk, so charge it here. Unlike the listener\n 952:\t\t\t * being closed, @sk is live and needs its lock.\n 953:\t\t\t */\n 954:\t\t\tfastopenq = \u0026inet_csk(sk)-\u003eicsk_accept_queue.fastopenq;\n"
} |
| 19/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9661 output: 25 thoughts: 165 Thoughts: **Analyzing the MPTCP Request Socket Cloning Patch** Okay, so I'm looking at this patch for `inet_reqsk_clone()`, specifically in the context of `SO_REUSEPORT` socket migration. The problem, as I understand it, is that when a listening socket is closed and its connection requests are moved to another listener in the reuseport group, the cloning process, handled by `inet_reqsk_clone()`, wasn't properly taking MPTCP-specific state into account. This means things like MPTCP token tracking and the managing of the `msk` reference weren't being cloned along with the request socket (`reqsk`). The patch seems to address this by introducing `mptcp_subflow_reqsk_clone` and `mptcp_token_move_request` to handle the MPTCP-specific aspects of the cloning. My immediate concern, as always, is whether this introduces any uninitialized memory vulnerabilities. I need to carefully review the `mptcp_subflow_request_sock` structure definition to understand what data it holds, and then I have to dig into `mptcp_token_init_request` to see how its components are initialized. Ensuring these components are properly initialized is critical to prevent potentially exploitable bugs down the road. This requires a meticulous walkthrough, paying close attention to data structure alignment and bitfield handling. The goal is to verify that these new functions ensure all MPTCP-related data is correctly copied during the cloning operation without leaking any uninitialized memory. |
| 20/3 | 2026/09/08 21:10 | tool | grepper |
0mArgs:{
"Expression": "struct mptcp_subflow_request_sock"
}Results: {
"Output": "net/mptcp/options.c=946=bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,\n--\nnet/mptcp/options.c-948-{\nnet/mptcp/options.c:949:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/options.c-950-\n--\nnet/mptcp/protocol.c=3713=struct sock *mptcp_sk_clone_init(const struct sock *sk,\n--\nnet/mptcp/protocol.c-3717-{\nnet/mptcp/protocol.c:3718:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/protocol.c-3719-\tstruct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);\n--\nnet/mptcp/protocol.h=495=struct csum_pseudo_header {\n--\nnet/mptcp/protocol.h-501-\nnet/mptcp/protocol.h:502:struct mptcp_subflow_request_sock {\nnet/mptcp/protocol.h-503-\tstruct\ttcp_request_sock sk;\n--\nnet/mptcp/protocol.h-522-\nnet/mptcp/protocol.h:523:static inline struct mptcp_subflow_request_sock *\nnet/mptcp/protocol.h-524-mptcp_subflow_rsk(const struct request_sock *rsk)\nnet/mptcp/protocol.h-525-{\nnet/mptcp/protocol.h:526:\treturn (struct mptcp_subflow_request_sock *)rsk;\nnet/mptcp/protocol.h-527-}\n--\nnet/mptcp/protocol.h=1085=int mptcp_token_new_connect(struct sock *ssk);\nnet/mptcp/protocol.h:1086:bool mptcp_token_accept(struct mptcp_subflow_request_sock *r,\nnet/mptcp/protocol.h-1087-\t\t\tstruct mptcp_sock *msk);\n--\nnet/mptcp/protocol.h=1357=static inline bool subflow_simultaneous_connect(struct sock *sk)\n--\nnet/mptcp/protocol.h-1365-#ifdef CONFIG_SYN_COOKIES\nnet/mptcp/protocol.h:1366:void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/protocol.h-1367-\t\t\t\t struct sk_buff *skb);\nnet/mptcp/protocol.h:1368:bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/protocol.h-1369-\t\t\t\t\tstruct sk_buff *skb);\n--\nnet/mptcp/protocol.h=1372=static inline void\nnet/mptcp/protocol.h:1373:subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/protocol.h-1374-\t\t\t\t struct sk_buff *skb) {}\nnet/mptcp/protocol.h=1375=static inline bool\nnet/mptcp/protocol.h:1376:mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/protocol.h-1377-\t\t\t\t struct sk_buff *skb)\n--\nnet/mptcp/subflow.c=38=static void subflow_req_destructor(struct request_sock *req)\nnet/mptcp/subflow.c-39-{\nnet/mptcp/subflow.c:40:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-41-\n--\nnet/mptcp/subflow.c=50=void mptcp_subflow_reqsk_clone(struct request_sock *req,\n--\nnet/mptcp/subflow.c-52-{\nnet/mptcp/subflow.c:53:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c:54:\tstruct mptcp_subflow_request_sock *new_subflow_req;\nnet/mptcp/subflow.c-55-\tstruct mptcp_sock *msk;\n--\nnet/mptcp/subflow.c=96=static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)\n--\nnet/mptcp/subflow.c-104-/* validate received token and create truncated hmac and nonce for SYN-ACK */\nnet/mptcp/subflow.c:105:static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_req)\nnet/mptcp/subflow.c-106-{\n--\nnet/mptcp/subflow.c=120=static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)\nnet/mptcp/subflow.c-121-{\nnet/mptcp/subflow.c:122:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-123-\tstruct mptcp_sock *msk;\n--\nnet/mptcp/subflow.c=144=static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)\nnet/mptcp/subflow.c-145-{\nnet/mptcp/subflow.c:146:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-147-\n--\nnet/mptcp/subflow.c=183=static int subflow_check_req(struct request_sock *req,\n--\nnet/mptcp/subflow.c-187-\tstruct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);\nnet/mptcp/subflow.c:188:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-189-\tstruct mptcp_options_received mp_opt;\n--\nnet/mptcp/subflow.c=300=int mptcp_subflow_init_cookie_req(struct request_sock *req,\n--\nnet/mptcp/subflow.c-304-\tstruct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);\nnet/mptcp/subflow.c:305:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-306-\tstruct mptcp_options_received mp_opt;\n--\nnet/mptcp/subflow.c=783=EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);\n--\nnet/mptcp/subflow.c-785-/* validate hmac received in third ACK */\nnet/mptcp/subflow.c:786:static bool subflow_hmac_valid(const struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/subflow.c-787-\t\t\t const struct mptcp_options_received *mp_opt)\n--\nnet/mptcp/subflow.c=839=static struct sock *subflow_syn_recv_sock(const struct sock *sk,\n--\nnet/mptcp/subflow.c-848-\tstruct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);\nnet/mptcp/subflow.c:849:\tstruct mptcp_subflow_request_sock *subflow_req;\nnet/mptcp/subflow.c-850-\tstruct mptcp_options_received mp_opt;\n--\nnet/mptcp/subflow.c=2077=static void subflow_ulp_clone(const struct request_sock *req,\n--\nnet/mptcp/subflow.c-2080-{\nnet/mptcp/subflow.c:2081:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/subflow.c-2082-\tstruct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);\n--\nnet/mptcp/subflow.c=2168=static int subflow_ops_init(struct request_sock_ops *subflow_ops)\nnet/mptcp/subflow.c-2169-{\nnet/mptcp/subflow.c:2170:\tsubflow_ops-\u003eobj_size = sizeof(struct mptcp_subflow_request_sock);\nnet/mptcp/subflow.c-2171-\n--\nnet/mptcp/subflow.c=2217=void __init mptcp_subflow_v6_init(void)\nnet/mptcp/subflow.c-2218-{\nnet/mptcp/subflow.c:2219:\t/* In struct mptcp_subflow_request_sock, we assume the TCP request sock\nnet/mptcp/subflow.c-2220-\t * structures for v4 and v6 have the same size. It should not changed in\n--\nnet/mptcp/syncookies.c=59=static void mptcp_join_store_state(struct join_entry *entry,\nnet/mptcp/syncookies.c:60:\t\t\t\t const struct mptcp_subflow_request_sock *subflow_req)\nnet/mptcp/syncookies.c-61-{\n--\nnet/mptcp/syncookies.c-70-\nnet/mptcp/syncookies.c:71:void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/syncookies.c-72-\t\t\t\t struct sk_buff *skb)\n--\nnet/mptcp/syncookies.c-91- */\nnet/mptcp/syncookies.c:92:bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,\nnet/mptcp/syncookies.c-93-\t\t\t\t\tstruct sk_buff *skb)\n--\nnet/mptcp/token.c=48=static struct token_bucket *token_bucket(u32 token)\n--\nnet/mptcp/token.c-53-/* called with bucket lock held */\nnet/mptcp/token.c:54:static struct mptcp_subflow_request_sock *\nnet/mptcp/token.c-55-__token_lookup_req(struct token_bucket *t, u32 token)\nnet/mptcp/token.c-56-{\nnet/mptcp/token.c:57:\tstruct mptcp_subflow_request_sock *req;\nnet/mptcp/token.c-58-\tstruct hlist_nulls_node *pos;\n--\nnet/mptcp/token.c=108=int mptcp_token_new_request(struct request_sock *req)\nnet/mptcp/token.c-109-{\nnet/mptcp/token.c:110:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/token.c-111-\tstruct token_bucket *bucket;\n--\nnet/mptcp/token.c=190=void mptcp_token_move_request(struct request_sock *req,\n--\nnet/mptcp/token.c-192-{\nnet/mptcp/token.c:193:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/token.c:194:\tstruct mptcp_subflow_request_sock *new_subflow_req;\nnet/mptcp/token.c:195:\tstruct mptcp_subflow_request_sock *pos;\nnet/mptcp/token.c-196-\tstruct token_bucket *bucket;\n--\nnet/mptcp/token.c-229- */\nnet/mptcp/token.c:230:bool mptcp_token_accept(struct mptcp_subflow_request_sock *req,\nnet/mptcp/token.c-231-\t\t\tstruct mptcp_sock *msk)\nnet/mptcp/token.c-232-{\nnet/mptcp/token.c:233:\tstruct mptcp_subflow_request_sock *pos;\nnet/mptcp/token.c-234-\tstruct sock *sk = (struct sock *)msk;\n--\nnet/mptcp/token.c=401=void mptcp_token_destroy_request(struct request_sock *req)\nnet/mptcp/token.c-402-{\nnet/mptcp/token.c:403:\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\nnet/mptcp/token.c:404:\tstruct mptcp_subflow_request_sock *pos;\nnet/mptcp/token.c-405-\tstruct token_bucket *bucket;\n--\nnet/mptcp/token_test.c-5-\nnet/mptcp/token_test.c:6:static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)\nnet/mptcp/token_test.c-7-{\nnet/mptcp/token_test.c:8:\tstruct mptcp_subflow_request_sock *req;\nnet/mptcp/token_test.c-9-\nnet/mptcp/token_test.c:10:\treq = kunit_kzalloc(test, sizeof(struct mptcp_subflow_request_sock),\nnet/mptcp/token_test.c-11-\t\t\t GFP_USER);\n--\nnet/mptcp/token_test.c=18=static void mptcp_token_test_req_basic(struct kunit *test)\nnet/mptcp/token_test.c-19-{\nnet/mptcp/token_test.c:20:\tstruct mptcp_subflow_request_sock *req = build_req_sock(test);\nnet/mptcp/token_test.c-21-\tstruct mptcp_sock *null_msk = NULL;\n--\nnet/mptcp/token_test.c=94=static void mptcp_token_test_accept(struct kunit *test)\nnet/mptcp/token_test.c-95-{\nnet/mptcp/token_test.c:96:\tstruct mptcp_subflow_request_sock *req = build_req_sock(test);\nnet/mptcp/token_test.c-97-\tstruct mptcp_sock *msk = build_msk(test);\n--\nnet/mptcp/token_test.c=113=static void mptcp_token_test_destroyed(struct kunit *test)\nnet/mptcp/token_test.c-114-{\nnet/mptcp/token_test.c:115:\tstruct mptcp_subflow_request_sock *req = build_req_sock(test);\nnet/mptcp/token_test.c-116-\tstruct mptcp_sock *msk = build_msk(test);\n"
} |
| 21/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 14412 output: 37 thoughts: 32 Thoughts: Okay, here's my take on those thoughts, framed as an expert's inner monologue: **Diving into the mptcp_subflow_request_sock Structure** Right, let's get down to brass tacks. I'm thinking, before I go any further, I need to refresh my memory and make sure I'm crystal clear on the definition of the `struct mptcp_subflow_request_sock`. Where better to start than the authoritative source – the header file, `net/mptcp/protocol.h`, right? I need a solid understanding of this structure to make any meaningful progress with this aspect of MPTCP. No sense in winging it when the precise definitions are right at my fingertips. Let's see what's what. |
| 22/3 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/mptcp/protocol.h",
"FirstLine": 500,
"LineCount": 35
}Results: {
"Contents": " 500:\t};\n 501:\t\n 502:\tstruct mptcp_subflow_request_sock {\n 503:\t\tstruct\ttcp_request_sock sk;\n 504:\t\tu16\tmp_capable : 1,\n 505:\t\t\tmp_join : 1,\n 506:\t\t\tbackup : 1,\n 507:\t\t\trequest_bkup : 1,\n 508:\t\t\tcsum_reqd : 1,\n 509:\t\t\tallow_join_id0 : 1;\n 510:\t\tu8\tlocal_id;\n 511:\t\tu8\tremote_id;\n 512:\t\tu64\tlocal_key;\n 513:\t\tu64\tidsn;\n 514:\t\tu32\ttoken;\n 515:\t\tu32\tssn_offset;\n 516:\t\tu64\tthmac;\n 517:\t\tu32\tlocal_nonce;\n 518:\t\tu32\tremote_nonce;\n 519:\t\tstruct mptcp_sock\t*msk;\n 520:\t\tstruct hlist_nulls_node token_node;\n 521:\t};\n 522:\t\n 523:\tstatic inline struct mptcp_subflow_request_sock *\n 524:\tmptcp_subflow_rsk(const struct request_sock *rsk)\n 525:\t{\n 526:\t\treturn (struct mptcp_subflow_request_sock *)rsk;\n 527:\t}\n 528:\t\n 529:\tstruct mptcp_delegated_action {\n 530:\t\tstruct napi_struct napi;\n 531:\t\tlocal_lock_t bh_lock;\n 532:\t\tstruct list_head head;\n 533:\t};\n 534:\t\n"
} |
| 23/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 15152 output: 23 thoughts: 1038 Thoughts: **Analyzing the `inet_reqsk_clone` Process with MPTCP Subflows** Okay, let's break down this `inet_reqsk_clone` function, focusing on the MPTCP subflow context. I need to understand how the request socket is cloned and how MPTCP-specific data is handled. First, within `inet_reqsk_clone`, the code allocates a new `request_sock` (`nreq`) using `kmem_cache_alloc`. Crucially, it uses `req->rsk_ops->slab`, which, in the MPTCP subflow case, is configured to allocate space for `struct mptcp_subflow_request_sock`. I see that a `memcpy` is performed. It copies the initial part of the `struct sock` fields from the original (`req_sk`) to the new one (`nreq_sk`). Then, it uses `unsafe_memcpy` to copy the remaining MPTCP-specific fields beyond the `struct sock` structure. This is based on the size defined by `req->rsk_ops->obj_size`, which, as I noted, equals `sizeof(struct mptcp_subflow_request_sock)` when MPTCP subflows are involved. This means the allocated memory is larger than `struct sock` and `unsafe_memcpy` copies the remaining part, which makes sense. Next, there's a check using `rsk_is_mptcp(req)` to determine if this is an MPTCP subflow. If it is, the code calls `mptcp_subflow_reqsk_clone`. This function seems critical for handling the MPTCP-specific state. Inside `mptcp_subflow_reqsk_clone`, I'm looking at the core logic: the goal is to initialize the MPTCP-specific part of the cloned request. `mptcp_subflow_rsk` is used to get pointers to the `mptcp_subflow_request_sock` structures for both the original (`req`) and the new (`new_req`) request socks. The code appears to be ensuring that it doesn't try to increase the reference count of the socket if the reference count is already zero. Then, it attempts to increment the reference count of the associated `mptcp_sock` (`msk`) using `refcount_inc_not_zero_acquire`. This suggests a potential shared ownership or a dependency relationship between the request socket and a master MPTCP socket. There's also a check using `READ_ONCE` to ensure the value of `msk` hasn't changed during the operation, and if it has, the code decrements the reference count and sets `msk` to NULL. Finally, it assigns the `msk` (possibly NULL if no valid socket exists) to the new subflow request. Then it calls `mptcp_token_move_request` to move token-related data from the original request to the new clone. `mptcp_token_move_request` seems to manage token buckets related to flow control or connection establishment. It checks if the token node for the subflow request is unhashed. If it is, `mptcp_token_init_request` is called, which will likely handle initializing this token data structure. If not, it retrieves the `token_bucket`. The code takes a spinlock to protect shared access to the bucket. Inside the lock, it re-checks if the token node is unhashed. If it still is, it calls `mptcp_token_init_request`. Otherwise, it finds the position of the old `token` using the bucket's lookup. It then tries to replace the existing `token` with the new one using `hlist_nulls_replace_init_rcu`, but only if the found position matches the existing one. Otherwise, it calls `mptcp_token_init_request` again, implying a fallback initialization if the replacement fails. Now I need to investigate `mptcp_token_init_request` to fully grasp the token management scheme. |
| 24/3 | 2026/09/08 21:10 | tool | grepper |
0mArgs:{
"Expression": "mptcp_token_init_request"
}Results: {
"Output": "net/mptcp/protocol.h=1075=void __init mptcp_token_init(void);\nnet/mptcp/protocol.h:1076:static inline void mptcp_token_init_request(struct request_sock *req)\nnet/mptcp/protocol.h-1077-{\n--\nnet/mptcp/subflow.c=144=static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)\n--\nnet/mptcp/subflow.c-152-\tsubflow_req-\u003emsk = NULL;\nnet/mptcp/subflow.c:153:\tmptcp_token_init_request(req);\nnet/mptcp/subflow.c-154-}\n--\nnet/mptcp/token.c=190=void mptcp_token_move_request(struct request_sock *req,\n--\nnet/mptcp/token.c-200-\tif (hlist_nulls_unhashed_lockless(\u0026subflow_req-\u003etoken_node)) {\nnet/mptcp/token.c:201:\t\tmptcp_token_init_request(new_req);\nnet/mptcp/token.c-202-\t\treturn;\n--\nnet/mptcp/token.c-207-\tif (hlist_nulls_unhashed(\u0026subflow_req-\u003etoken_node)) {\nnet/mptcp/token.c:208:\t\tmptcp_token_init_request(new_req);\nnet/mptcp/token.c-209-\t} else {\n--\nnet/mptcp/token.c-214-\t\telse\nnet/mptcp/token.c:215:\t\t\tmptcp_token_init_request(new_req);\nnet/mptcp/token.c-216-\t}\n--\nnet/mptcp/token_test.c=6=static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)\n--\nnet/mptcp/token_test.c-12-\tKUNIT_EXPECT_NOT_ERR_OR_NULL(test, req);\nnet/mptcp/token_test.c:13:\tmptcp_token_init_request((struct request_sock *)req);\nnet/mptcp/token_test.c-14-\tsock_net_set((struct sock *)req, \u0026init_net);\n"
} |
| 25/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 17724 output: 38 thoughts: 18 Thoughts: Here's a breakdown of the implementation of `mptcp_token_init_request`, focusing on what's important for someone with your expertise: **Diving into `mptcp_token_init_request`** Alright, let's dissect this. My first thought is to understand the context. This is the function responsible for... initiating the token exchange for MPTCP, obviously. Crucial for establishing that subflow with the associated control information. I'm immediately looking for the data structures involved – what kind of `struct`s are we dealing with here? Probably some sort of connection context (`struct mptcp_sock`, perhaps?) and token-related data (`struct mptcp_token` or something similar, likely). I need to understand how the token itself is generated, and crucially, how its initial validity period is determined. Is it based on a timer, or a negotiated value? What are the security considerations? Are we using cryptographic primitives for token protection? Key exchange is always something to focus on. Then, I'm thinking about the control flow. How does this request integrate with the overall MPTCP connection establishment process? Is it called synchronously during connection setup, or is it part of a later negotiation? How are errors handled? I'm anticipating error codes for things like resource limitations, protocol violations, or security issues during token generation. I expect there to be some interaction with the underlying TCP stack, probably to signal the need for a token or to send the initial request on the control flow. I also want to see how this implementation handles potential race conditions or concurrency issues. Is there locking involved, especially if multiple threads or processes might be attempting to establish subflows concurrently? I'm also considering how the token is subsequently used. The init request is only the beginning. How are subsequent token requests handled, and how does the system maintain state? What kind of optimizations are implemented for different MPTCP connection scenarios? Finally, what are the implications on performance? Token exchange is a trade-off: overhead versus the benefits of subflow creation and load balancing. I'd like to see if any optimizations are in place (e.g., caching, pre-calculation, etc.). And of course, I'm keen to evaluate the overall security and robustness of the implementation. So, let's get into the code and see how it is working. |
| 26/3 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/mptcp/protocol.h",
"FirstLine": 1074,
"LineCount": 15
}Results: {
"Contents": "1074:\t\n1075:\tvoid __init mptcp_token_init(void);\n1076:\tstatic inline void mptcp_token_init_request(struct request_sock *req)\n1077:\t{\n1078:\t\tmptcp_subflow_rsk(req)-\u003etoken_node.pprev = NULL;\n1079:\t}\n1080:\t\n1081:\tint mptcp_token_new_request(struct request_sock *req);\n1082:\tvoid mptcp_token_move_request(struct request_sock *req,\n1083:\t\t\t\t struct request_sock *new_req);\n1084:\tvoid mptcp_token_destroy_request(struct request_sock *req);\n1085:\tint mptcp_token_new_connect(struct sock *ssk);\n1086:\tbool mptcp_token_accept(struct mptcp_subflow_request_sock *r,\n1087:\t\t\t\tstruct mptcp_sock *msk);\n1088:\tbool mptcp_token_exists(u32 token);\n"
} |
| 27/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 18575 output: 38 thoughts: 60 Thoughts: **Examining the MPTCP Socket Cloning Implementation** Okay, let's dive into this `mptcp_sk_clone_destroy` function. I want to make sure the memory management is solid there, especially with regard to any potential error scenarios. And then I need to look closely at the initialization, specifically `mptcp_sk_clone_init()`. Time to go digging in `net/mptcp/protocol.c` and see how this all hangs together. I need to understand the interaction of these functions, to see if there is an area of possible concern. |
| 28/3 | 2026/09/08 21:10 | tool | read-file |
0mArgs:{
"File": "net/mptcp/protocol.c",
"FirstLine": 3710,
"LineCount": 80
}Results: {
"Contents": "3710:\t\tinet_csk_destroy_sock(nsk);\n3711:\t}\n3712:\t\n3713:\tstruct sock *mptcp_sk_clone_init(const struct sock *sk,\n3714:\t\t\t\t\t const struct mptcp_options_received *mp_opt,\n3715:\t\t\t\t\t struct sock *ssk,\n3716:\t\t\t\t\t struct request_sock *req)\n3717:\t{\n3718:\t\tstruct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);\n3719:\t\tstruct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);\n3720:\t\tstruct mptcp_subflow_context *subflow;\n3721:\t\tstruct mptcp_sock *msk;\n3722:\t\n3723:\t\tif (!nsk)\n3724:\t\t\treturn NULL;\n3725:\t\n3726:\t#if IS_ENABLED(CONFIG_MPTCP_IPV6)\n3727:\t\tif (nsk-\u003esk_family == AF_INET6)\n3728:\t\t\tinet_sk(nsk)-\u003epinet6 = mptcp_inet6_sk(nsk);\n3729:\t#endif\n3730:\t\n3731:\t\t__mptcp_init_sock(nsk);\n3732:\t\n3733:\t#if IS_ENABLED(CONFIG_MPTCP_IPV6)\n3734:\t\tif (nsk-\u003esk_family == AF_INET6)\n3735:\t\t\tmptcp_copy_ip6_options(nsk, sk);\n3736:\t\telse\n3737:\t#endif\n3738:\t\t\tmptcp_copy_ip_options(nsk, sk);\n3739:\t\n3740:\t\tmsk = mptcp_sk(nsk);\n3741:\t\tWRITE_ONCE(msk-\u003elocal_key, subflow_req-\u003elocal_key);\n3742:\t\tWRITE_ONCE(msk-\u003etoken, subflow_req-\u003etoken);\n3743:\t\tmsk-\u003ein_accept_queue = 1;\n3744:\t\tWRITE_ONCE(msk-\u003efully_established, false);\n3745:\t\tif (mp_opt-\u003esuboptions \u0026 OPTION_MPTCP_CSUMREQD)\n3746:\t\t\tWRITE_ONCE(msk-\u003ecsum_enabled, true);\n3747:\t\n3748:\t\tWRITE_ONCE(msk-\u003ewrite_seq, subflow_req-\u003eidsn + 1);\n3749:\t\tWRITE_ONCE(msk-\u003esnd_nxt, msk-\u003ewrite_seq);\n3750:\t\tWRITE_ONCE(msk-\u003esnd_una, msk-\u003ewrite_seq);\n3751:\t\tWRITE_ONCE(msk-\u003ewnd_end, msk-\u003esnd_nxt + tcp_sk(ssk)-\u003esnd_wnd);\n3752:\t\tmsk-\u003esetsockopt_seq = mptcp_sk(sk)-\u003esetsockopt_seq;\n3753:\t\tmptcp_init_sched(msk, mptcp_sk(sk)-\u003esched);\n3754:\t\n3755:\t\t/* passive msk is created after the first/MPC subflow */\n3756:\t\tmsk-\u003esubflow_id = 2;\n3757:\t\n3758:\t\tsock_reset_flag(nsk, SOCK_RCU_FREE);\n3759:\t\tsecurity_inet_csk_clone(nsk, req);\n3760:\t\n3761:\t\t/* this can't race with mptcp_close(), as the msk is\n3762:\t\t * not yet exposted to user-space\n3763:\t\t */\n3764:\t\tmptcp_set_state(nsk, TCP_ESTABLISHED);\n3765:\t\n3766:\t\t/* The msk maintain a ref to each subflow in the connections list */\n3767:\t\tWRITE_ONCE(msk-\u003efirst, ssk);\n3768:\t\tsubflow = mptcp_subflow_ctx(ssk);\n3769:\t\tlist_add(\u0026subflow-\u003enode, \u0026msk-\u003econn_list);\n3770:\t\tsock_hold(ssk);\n3771:\t\n3772:\t\t/* set msk addresses early to ensure mptcp_pm_get_local_id()\n3773:\t\t * uses the correct data\n3774:\t\t */\n3775:\t\tmptcp_copy_inaddrs(nsk, ssk);\n3776:\t\n3777:\t\tmptcp_rcv_space_init(msk, ssk);\n3778:\t\tmsk-\u003ercvq_space.time = mptcp_stamp();\n3779:\t\n3780:\t\tif (!mptcp_token_accept(subflow_req, msk)) {\n3781:\t\t\tlist_del_init(\u0026subflow-\u003enode);\n3782:\t\t\tWRITE_ONCE(msk-\u003efirst, NULL);\n3783:\t\t\tsock_put(ssk);\n3784:\t\t\tmptcp_sk_clone_destroy(nsk);\n3785:\t\t\treturn NULL;\n3786:\t\t}\n3787:\t\n3788:\t\tif (mp_opt-\u003esuboptions \u0026 OPTION_MPTCP_MPC_ACK)\n3789:\t\t\t__mptcp_subflow_fully_established(msk, subflow, mp_opt);\n"
} |
| 29/3 | 2026/09/08 21:10 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 20193 output: 191 thoughts: 963 Thoughts: **KMSAN Assessment: MPTCP Request Socket Cloning During Reuseport Migration** Alright, let's break this down systematically. I need to determine if this patch necessitates KMSAN or if KASAN is sufficient. The core of this patch involves the cloning of MPTCP request sockets during a reuseport migration, specifically when dealing with subflows. The key operations involve transferring MultiPath TCP (MPTCP) specific data, primarily `msk` references and token table entries, from the original request socket to its clone. Failure scenarios within `mptcp_token_accept` are also gracefully handled. My initial assessment is to look for potential KMSAN triggers. We know KMSAN concerns itself with uninitialized memory reads, particularly those that leak information to user space or that affect control flow. Looking at the criteria, I'm checking for kernel structures passed to user space, conditional logic based on potentially uninitialized variables, uninitialized reads, and any bounds checks that could expose uninitialized data. The code changes here involve `inet_reqsk_clone()`, which calls `mptcp_subflow_reqsk_clone()` to handle the MPTCP specific stuff. Within that, we have `mptcp_token_move_request()` and `mptcp_token_accept()`, with proper locking and list manipulation. Error handling in `mptcp_token_accept` is also included. There's also `mptcp_sk_clone_init()` in case of failure. Now, let's run through the potential KMSAN concerns: * **Uninitialized Variables?** No. The changes don't introduce any new stack or heap allocations that leave fields uninitialized and then expose them to user space or conditional branching. `inet_reqsk_clone()` is allocating a `nreq` from the slab cache, and then copying the contents from a source `req` using `memcpy`. The new `mptcp_token_move_request` initializes the `new_subflow_req->token_node`. The allocations are either fully initialized or copied from known-good data. No new uninitialized memory is introduced. * **Info Leaks?** No. Nothing new is being copied to user space, or created on the stack, and copied to user space. * **Uninitialized Buffer Reads?** No. The code isn't reading from any uninitialized buffers, or potentially accessing uninitialized data through incorrect bounds checks. Therefore, given the nature of the modifications, the potential risks lie in concurrency issues: RCU, refcounting, locking, use-after-free, and error handling. However, these are precisely the kinds of bugs that KASAN, LOCKDEP, and standard kernel debugging tools, such as refcount checkers, PROVE\_LOCKING, are built to catch. My conclusion is clear: **KMSAN is not needed here.** This patch primarily deals with concurrency concerns related to socket cloning, data transfer, and refcounting. These issues are thoroughly addressed by the existing KASAN, LOCKDEP, and refcount checking infrastructure. The patch doesn't introduce or alter any risk of uninitialized memory use or information leaks. We're safe with KASAN. |
| 30/3 | 2026/09/08 21:11 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch fixes MPTCP request socket cloning during reuseport socket migration by safely handling msk socket refcounts, moving token hash table entries (mptcp_token_move_request), and properly cleaning up and falling back when mptcp_token_accept fails.\n\nThese changes involve concurrency, RCU safety, socket refcounting, and lifecycle/destruction state management. Any potential bugs in this area are use-after-free, refcounting issues, or locking/deadlock bugs, which are detected by KASAN, LOCKDEP, and standard kernel sanitizers. The patch does not introduce or modify uninitialized stack/heap allocations, memory copying to userspace, padding/info-leaks, or branching on uninitialized memory. Therefore, a dedicated KMSAN fuzzing session is not required.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch fixes MPTCP request socket cloning during reuseport socket migration by safely handling msk socket refcounts, moving token hash table entries (mptcp_token_move_request), and properly cleaning up and falling back when mptcp_token_accept fails.\n\nThese changes involve concurrency, RCU safety, socket refcounting, and lifecycle/destruction state management. Any potential bugs in this area are use-after-free, refcounting issues, or locking/deadlock bugs, which are detected by KASAN, LOCKDEP, and standard kernel sanitizers. The patch does not introduce or modify uninitialized stack/heap allocations, memory copying to userspace, padding/info-leaks, or branching on uninitialized memory. Therefore, a dedicated KMSAN fuzzing session is not required.",
"NeedsKMSAN": false
} |
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