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=1792605761; b=1IecARK7K025BKCZwAXY4aobjgt9Lwn8P+glzL+TOaEIo3toN0EdF4nTSa2LJb52D9TJ 6eiKPj6uqfUqP8dbZOTCMiq/zb5vduUNx3UDLyFDsoz3jXo2TXDV0G+7q00YXWyLOMVDZ RXuU4hiiPtqgGsnSrbVAQ+P1IXHUidi6N77tS45y/+InrQ02H4kgsLU4VLI8GEosfmgWP LCFimn4rwAYN8bFP9/KuOv58ZkvIouhzKFiq77gXR6FLrVgQPOcQZ0GLYJDPbfdftTnI3 lIAcYPGrYAtMY7kS7yLMp4VqZOYOwLmtuJ/LtT+DahoeUVCHf6bLhx0NP0yfOR1xtZw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792605761; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=e2alJIXSYK3LZK91rZBSjOS8qrL9zNkTpWnd8/jXosg=; b=hZMYx+cpqsqCK6Yx6IiEn3whqTMSeC5e2aCntGzOuzIraMJ3aSTtEV5kl+DcO6sDFEug qvN0rHDWW+gIxRao7QQwgqJS+2HR+qKs3acURO3d+ZR7kncbNGorxgNw7rbKYklKbFfKw qzzWH3jO+dbNVwSBemcAeky4vI3dQAquf98I/Ay0ldUWCTaBFC4Pn89MQHn2vDUlXREHh U+ZPPlTSw931R0LOSx7kNen5At7El3WebxcU/gIJh4xo1Ka21qCJ9cHWRo8k0a+DNic4J 7SCbN0Bv+zkkYepE3WEolT2As1JcYxyGXJgDmUZrL7v5hZEtVruGBmpAHXSgdKOm48Q== 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="LO64XtB/"; 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 76F78606A319 for ; Wed, 21 Oct 2026 18:02:41 +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=LO64XtB/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BCF31F000C1; Wed, 21 Oct 2026 18:02:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792605761; bh=e2alJIXSYK3LZK91rZBSjOS8qrL9zNkTpWnd8/jXosg=; h=Subject:To:Cc:From:Date; b=LO64XtB/PC7twcKpszKEf7AUTfVdf369cBO6Q9HZmLIjg8guXdp4//Ush3L1pONli zJhHth8Yc15DHgbXthSttXrynFIaemZpDE6JtnPNk3G6GuNFAWtiL0p3yL1m1j/G7b 5gIM36gzI8614FesA60ihBtJFjWAMTNxtOjoRSsw= Subject: FAILED: patch "[PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)" failed to apply to 5.15-stable tree To: blbllhy@gmail.com,edumazet@google.com,jiayuan.chen@linux.dev,kuba@kernel.org,leitao@debian.org,matttbe@kernel.org,xmei5@asu.edu Cc: From: Date: Wed, 21 Oct 2026 19:57:27 +0200 Message-ID: <2026102127-crept-debate-2807@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x 5271b79b7ad68dcb222e893773f92bdabf7750f3 # git commit -s git send-email --to '' --in-reply-to '2026102127-crept-debate-2807@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 5271b79b7ad68dcb222e893773f92bdabf7750f3 Mon Sep 17 00:00:00 2001 From: "Cen Zhang (Microsoft Security FORGE Labs)" Date: Thu, 27 Aug 2026 19:55:10 -0400 Subject: [PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) do_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding rcu_read_lock(). Since commit 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf"), icsk_ca_ops can point to dynamically allocated BPF struct_ops memory that may be freed concurrently via setsockopt(TCP_CONGESTION), leading to a use-after-free. BUG: KASAN: slab-use-after-free in _copy_to_user+0x37/0x60 Read of size 16 at addr ffff888013505260 by task exploit/149 _copy_to_user+0x37/0x60 do_tcp_getsockopt+0x158a/0x2460 (net/ipv4/tcp.c:4585) tcp_getsockopt+0x91/0xf0 __sys_getsockopt+0xf7/0x170 Fix this by holding rcu_read_lock() around the ca_ops->name access, using READ_ONCE() to load icsk_ca_ops, and copying the name to a stack buffer before releasing the lock. Also annotate the relevant icsk_ca_ops stores with WRITE_ONCE() to fix the accompanying KCSAN data-race issue. Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf") Suggested-by: Eric Dumazet Reported-by: Xiang Mei (Microsoft) Link: https://lore.kernel.org/all/20260821182449.79785-2-blbllhy@gmail.com/ Cc: AutonomousCodeSecurity@microsoft.com Cc: stable@vger.kernel.org Reviewed-by: Eric Dumazet Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) Reviewed-by: Jiayuan Chen Reviewed-by: Matthieu Baerts (NGI0) Reviewed-by: Breno Leitao Link: https://patch.msgid.link/d3f97f1acbf0010898148be6e6406e4b8b4a5c84.1787870710.git.blbllhy@gmail.com Signed-off-by: Jakub Kicinski diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 93d723d8c109..740999c9efff 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4576,16 +4576,24 @@ int do_tcp_getsockopt(struct sock *sk, int level, val = !inet_csk_in_pingpong_mode(sk); break; - case TCP_CONGESTION: + case TCP_CONGESTION: { + char ca_name[TCP_CA_NAME_MAX] = {}; + if (copy_from_sockptr(&len, optlen, sizeof(int))) return -EFAULT; len = min_t(unsigned int, len, TCP_CA_NAME_MAX); if (copy_to_sockptr(optlen, &len, sizeof(int))) return -EFAULT; - if (copy_to_sockptr(optval, icsk->icsk_ca_ops->name, len)) + + rcu_read_lock(); + memcpy(ca_name, READ_ONCE(icsk->icsk_ca_ops)->name, + sizeof(ca_name)); + rcu_read_unlock(); + + if (copy_to_sockptr(optval, ca_name, len)) return -EFAULT; return 0; - + } case TCP_ULP: if (copy_from_sockptr(&len, optlen, sizeof(int))) return -EFAULT; diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index e9f6c77e0631..8e83ef81fc18 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -223,7 +223,7 @@ void tcp_assign_congestion_control(struct sock *sk) ca = rcu_dereference(net->ipv4.tcp_congestion_control); if (unlikely(!bpf_try_module_get(ca, ca->owner))) ca = &tcp_reno; - icsk->icsk_ca_ops = ca; + WRITE_ONCE(icsk->icsk_ca_ops, ca); rcu_read_unlock(); memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); @@ -253,7 +253,7 @@ static void tcp_reinit_congestion_control(struct sock *sk, struct inet_connection_sock *icsk = inet_csk(sk); tcp_cleanup_congestion_control(sk); - icsk->icsk_ca_ops = ca; + WRITE_ONCE(icsk->icsk_ca_ops, ca); icsk->icsk_ca_setsockopt = 1; memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c index 274e628e7cf8..99f68c2992d0 100644 --- a/net/ipv4/tcp_dctcp.c +++ b/net/ipv4/tcp_dctcp.c @@ -111,7 +111,7 @@ __bpf_kfunc static void dctcp_init(struct sock *sk) /* No ECN support? Fall back to Reno. Also need to clear * ECT from sk since it is set during 3WHS for DCTCP. */ - inet_csk(sk)->icsk_ca_ops = &dctcp_reno; + WRITE_ONCE(inet_csk(sk)->icsk_ca_ops, &dctcp_reno); INET_ECN_dontxmit(sk); } diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index f3fa0b18eda0..0ddfd5af6e58 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -507,7 +507,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst) ca = tcp_ca_find_key(ca_key); if (likely(ca && bpf_try_module_get(ca, ca->owner))) { icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst); - icsk->icsk_ca_ops = ca; + WRITE_ONCE(icsk->icsk_ca_ops, ca); ca_got_dst = true; } rcu_read_unlock(); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c5ffffee4349..d960e3de7d50 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -4092,7 +4092,7 @@ static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst) if (likely(ca && bpf_try_module_get(ca, ca->owner))) { bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner); icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst); - icsk->icsk_ca_ops = ca; + WRITE_ONCE(icsk->icsk_ca_ops, ca); } rcu_read_unlock(); }