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Wed, 26 Aug 2026 10:14:12 -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, matttbe@kernel.org, martineau@kernel.org, geliang@kernel.org, yhs@fb.com, kafai@fb.com, andriin@fb.com, ast@kernel.org, netdev@vger.kernel.org, mptcp@lists.linux.dev, 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 v2 2/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO) Date: Wed, 26 Aug 2026 13:13:44 -0400 Message-ID: <20260826171344.4133-3-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260826171344.4133-1-blbllhy@gmail.com> References: <20260826171344.4133-1-blbllhy@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Cen Zhang (Microsoft Security FORGE Labs)" 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(), and using READ_ONCE() to load the icsk_ca_ops pointer. Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf") Suggested-by: Eric Dumazet Cc: AutonomousCodeSecurity@microsoft.com Cc: stable@vger.kernel.org Assisted-by: GitHub-Copilot:claude-opus-4.6 Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) --- Link: https://lore.kernel.org/all/20260821182449.79785-3-blbllhy@gmail.com/ (v1) Changes in v2: - Add READ_ONCE() for the icsk_ca_ops load. --- net/ipv4/tcp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 4918f48ba76d..c45776d3ed90 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; - ca_ops = icsk->icsk_ca_ops; + rcu_read_lock(); + ca_ops = READ_ONCE(icsk->icsk_ca_ops); if (ca_ops && ca_ops->get_info) sz = ca_ops->get_info(sk, ~0U, &attr, &info); + rcu_read_unlock(); len = min_t(unsigned int, len, sz); if (copy_to_sockptr(optlen, &len, sizeof(int))) -- 2.55.0