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Fri, 21 Aug 2026 11:25:17 -0700 (PDT) From: "Cen Zhang (Microsoft)" To: edumazet@google.com, ncardwell@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: kuniyu@google.com, horms@kernel.org, yhs@fb.com, kafai@fb.com, andriin@fb.com, ast@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, xmei5@asu.edu, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com, stable@vger.kernel.org Subject: [PATCH net 1/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) Date: Fri, 21 Aug 2026 14:24:48 -0400 Message-ID: <20260821182449.79785-2-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260821182449.79785-1-blbllhy@gmail.com> References: <20260821182449.79785-1-blbllhy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 and copying the name to a stack buffer before releasing the lock. Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf") Reported-by: AutonomousCodeSecurity@microsoft.com Reported-by: Xiang Mei (Microsoft) Reported-by: Cen Zhang (Microsoft) Cc: stable@vger.kernel.org Signed-off-by: Cen Zhang (Microsoft) --- The unsynchronized icsk_ca_ops load also constitutes a data race. READ_ONCE()/WRITE_ONCE() annotations are intentionally left to a separate change; related TCP annotation work is available at: https://lore.kernel.org/all/20260416200319.3608680-1-edumazet@google.com/ net/ipv4/tcp.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index b4237d0e994d..7360ff718f1d 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4577,16 +4577,23 @@ int do_tcp_getsockopt(struct sock *sk, int level, val =3D !inet_csk_in_pingpong_mode(sk); break; =20 - case TCP_CONGESTION: + case TCP_CONGESTION: { + char ca_name[TCP_CA_NAME_MAX] =3D {}; + if (copy_from_sockptr(&len, optlen, sizeof(int))) return -EFAULT; len =3D 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, 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; --=20 2.55.0 From nobody Mon Sep 28 12:33:12 2026 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8378A3845A4 for ; Fri, 21 Aug 2026 18:25:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.43 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787336736; cv=none; b=GGRWvF43IHOYXiaoX7+nG6zv3BXE67vsFUDASWzCtNv1KBhMg82CL8v21JByNKRxZ1bIK5UUQ2o2gneYSxvxWfNaeUx2DuZOwdbRogbAd+tWfnJiXZdCnZkr1A2jk8JQ2UHpKuXLJ28KQS+/KCXpCGkpLW3wQqFbrWsFJBjFfvc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787336736; c=relaxed/simple; bh=+jEjnMMcx1Z4BgKf7iCzxIErD7+9CDxFlLEG/VspZIM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; 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Fri, 21 Aug 2026 11:25:31 -0700 (PDT) From: "Cen Zhang (Microsoft)" To: edumazet@google.com, ncardwell@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: kuniyu@google.com, horms@kernel.org, yhs@fb.com, kafai@fb.com, andriin@fb.com, ast@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, xmei5@asu.edu, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com, stable@vger.kernel.org Subject: [PATCH net 2/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO) Date: Fri, 21 Aug 2026 14:24:49 -0400 Message-ID: <20260821182449.79785-3-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260821182449.79785-1-blbllhy@gmail.com> References: <20260821182449.79785-1-blbllhy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" do_tcp_getsockopt() reads icsk->icsk_ca_ops and dereferences the get_info function pointer without rcu_read_lock(). With BPF struct_ops congestion control, ca_ops can point to dynamically allocated memory that is freed concurrently, resulting in a use-after-free when the kernel dereferences or calls through the stale pointer. BUG: KASAN: slab-use-after-free in do_tcp_getsockopt+0x2037/0x23e0 Read of size 8 at addr ffff888013701258 by task exploit/149 do_tcp_getsockopt+0x2037/0x23e0 (net/ipv4/tcp.c:4564) tcp_getsockopt+0x91/0xf0 __sys_getsockopt+0xf7/0x170 Fix this by wrapping the ca_ops load and get_info call within rcu_read_lock()/rcu_read_unlock(). Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf") Reported-by: AutonomousCodeSecurity@microsoft.com Reported-by: Cen Zhang (Microsoft) Cc: stable@vger.kernel.org Signed-off-by: Cen Zhang (Microsoft) --- The unsynchronized icsk_ca_ops load also constitutes a data race. READ_ONCE()/WRITE_ONCE() annotations are intentionally left to a separate change; related TCP annotation work is available at: https://lore.kernel.org/all/20260416200319.3608680-1-edumazet@google.com/ net/ipv4/tcp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 7360ff718f1d..43ccd2d37f9c 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4562,9 +4562,11 @@ int do_tcp_getsockopt(struct sock *sk, int level, if (copy_from_sockptr(&len, optlen, sizeof(int))) return -EFAULT; =20 + rcu_read_lock(); ca_ops =3D icsk->icsk_ca_ops; if (ca_ops && ca_ops->get_info) sz =3D ca_ops->get_info(sk, ~0U, &attr, &info); + rcu_read_unlock(); =20 len =3D min_t(unsigned int, len, sz); if (copy_to_sockptr(optlen, &len, sizeof(int))) --=20 2.55.0