From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793801991; b=F93NjBxXg8flML9eoopLU+RXt/PXaYgxI5JeYdyDL7lZqprh77FCmAgJhuVlRaFxqm+n 6imgL+hAQGCeLl3NjSbNP2EO9iEer+1glIXYQkRfMjM9uwGa5HSjjR0YCYCaaB4OID5Cy NZPIgNa9filwvWytdJqC+OY8ugmvpRE877Ibbx9ukgTDDFvFAOGf+iFTqHwML++VIVkR+ 3VIcZ1iqnm7EodPJRf6WaRzaYdybu+0b83pVgwZZsDg08dnSPGSX104t63O5/8JXKQjWr KyGxLWCdbpqV1UG71Yy8ENQGLq1YsWmrxt5Y9c7F6yoX+iYjwr5UPgj7HCYag+Oqgog== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793801991; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=ZaGpG5+A1JEAMi504z5da7YUUqKRMUpOnyF7uHlvEjU=; b=uvvcK6C4EwrReCQd0XXCM89AUxD3MJAdpBNeW8SAGiC/kAYCYIBmAS3XAmeQi7UTk1Is QrQVD9EkDzpQ1u7ob1p1fvqi3Q56dtaRGpj4y9n62CzF/pzUCOD/SBlKrspWQ1nl3bQ+k FUs8BjcGuYb6/fFd7xqDaYXT+3pWOgNIYov1AxZbBb1rBzk8Mtdfai81r2ZLisK2zwRSG UVTTikIAsoOaccB3shNMza9r12JedIXpRt6LckLd1Vs0DK3PE5I7/TobQb6Hj8UZ8N9tz q3C+gjn0PC7vsNwXEE/6vacLwZV1mgcmlIoG476AWN/mLsOPVlGoyhYM4DpVszClDCg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=iwLCGYPS; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 660C4606A31B for ; Wed, 4 Nov 2026 14:19:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=iwLCGYPS Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA3DE1F00919; Wed, 4 Nov 2026 14:19:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793801991; bh=ZaGpG5+A1JEAMi504z5da7YUUqKRMUpOnyF7uHlvEjU=; h=Subject:To:Cc:From:Date; b=iwLCGYPSEXBKs+ivBrjnvknPCAITWHilTCzgYZ0rjkFGYigMiZGQCtHTCTkWUym7a B3ZHPS2jHPNHapag4lVSb5tZnrWT3UEt9Xw+7BvbIxJYhYVXpMTFFPOin6A9nQdTpV eTNSSk5RdfeAG3Naj5t3oiY0sLtHtXRDCe2ZHv30= Subject: FAILED: patch "[PATCH] mptcp: hold MP_JOIN msk ref when cloning reqsk" failed to apply to 6.12-stable tree To: caoruide123@gmail.com,david.lee@trailofbits.com,kuba@kernel.org,kylebot@openai.com,matttbe@kernel.org,vega@nebusec.ai,weir@nebusec.ai Cc: From: Date: Wed, 04 Nov 2026 15:19:49 +0100 Message-ID: <2026110449-profile-pessimism-5c6f@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x c9c90cf437a9e6597611b6d3aad6e255fad22867 # git commit -s git send-email --to '' --in-reply-to '2026110449-profile-pessimism-5c6f@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From c9c90cf437a9e6597611b6d3aad6e255fad22867 Mon Sep 17 00:00:00 2001 From: Ruide Cao Date: Tue, 13 Oct 2026 16:29:21 +0200 Subject: [PATCH] mptcp: hold MP_JOIN msk ref when cloning reqsk TCP request migration clones pending request sockets with inet_reqsk_clone(). For MPTCP MP_JOIN requests this byte-copies subflow_req->msk, but the clone does not own a reference. The original and cloned requests can consequently drop the same msk reference, leaving one request with a dangling pointer. This manifests as a KASAN slab-use-after-free in subflow_req_destructor(): BUG: KASAN: slab-use-after-free in subflow_req_destructor (net/mptcp/subflow.c:45) Write of size 4 at addr ff1100010e008d40 by task swapper/0/0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc5-00353-gc27e36054537 #10 PREEMPT(full) Call Trace: subflow_req_destructor (net/mptcp/subflow.c:45) subflow_v4_req_destructor (net/mptcp/subflow.c:694) __reqsk_free (net/ipv4/inet_connection_sock.c:906) reqsk_timer_handler (include/net/request_sock.h:137 net/ipv4/inet_connection_sock.c:1147) Allocated by task 10014: sk_prot_alloc (net/core/sock.c:2246) sk_clone (net/core/sock.c:2488) mptcp_sk_clone_init (include/net/sock.h:1848 net/mptcp/protocol.c:3564) subflow_syn_recv_sock (net/mptcp/subflow.c:883) tcp_check_req (net/ipv4/tcp_minisocks.c:934) Freed by task 0: slab_free_after_rcu_debug (include/linux/kasan.h:235 mm/slub.c:2677 mm/slub.c:6439) rcu_core (kernel/rcu/tree.c:2645 kernel/rcu/tree.c:2897) Last potentially related work creation: kmem_cache_free (mm/slub.c:2638 mm/slub.c:6377 mm/slub.c:6504) __sk_destruct (net/core/sock.c:2289 net/core/sock.c:2391) sk_destruct (net/core/sock.c:2419) __sk_free (net/core/sock.c:2430) sk_free (net/core/sock.c:2441) mptcp_close (include/net/sock.h:2020 net/mptcp/protocol.c:3399) inet_release (net/ipv4/af_inet.c:442) The buggy address belongs to the cache MPTCP of size 2968 The buggy address is 128 bytes inside a freed 2968-byte region A non-NULL subflow_req->msk means that the request owns one reference. The third ACK can concurrently transfer the original request reference to the child and release it, so taking an unconditional hold on the copied pointer is unsafe. MPTCP sockets use SLAB_TYPESAFE_BY_RCU and all current inet_reqsk_clone() callers run in an RCU read-side critical section. Document and lockdep-check that calling-context requirement. Read the pointer from the original request and acquire a reference only if it is still live. Use refcount_inc_not_zero_acquire() so the subsequent ownership validation cannot be reordered before the try-get, then re-read the original request to verify that it still owns the same msk. If either check fails, clear the clone pointer; otherwise its normal destructor balances the new reference. Mark the ownership-transfer store with WRITE_ONCE() to match the lockless reads. The following patch completes the clone fixup for MP_CAPABLE token ownership. Both patches carry the same Fixes tag and are required for stable backports. Fixes: c905dee62232 ("tcp: Migrate TCP_NEW_SYN_RECV requests at retransmitting SYN+ACKs.") Cc: stable@vger.kernel.org Reported-by: Kyle Zeng Reported-by: David Lee Reported-by: Vega Closes: https://lore.kernel.org/all/20260804095051.715355-1-david.lee@trailofbits.com/ Signed-off-by: Ruide Cao Signed-off-by: Ren Wei Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20261013-net-mptcp-misc-fixes-7-3-rc8-v1-3-932c9b182fc7@kernel.org Signed-off-by: Jakub Kicinski diff --git a/include/net/mptcp.h b/include/net/mptcp.h index 485d55b66ea6..ad7005b574bb 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 6a30f1138454..c6f8011200a0 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include @@ -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/subflow.c b/net/mptcp/subflow.c index f0a6725d2c37..3139a9ab2853 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -47,6 +47,39 @@ 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; +} + static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2, void *hmac) { @@ -927,7 +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)) {