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Fri, 21 Aug 2026 11:25:03 -0700 (PDT) Received: from localhost.localdomain ([2001:4898:a800:1012:54e3:69b5:423e:871a]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-395c45539a1sm4243013a91.3.2026.08.21.11.24.59 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 21 Aug 2026 11:25:02 -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 Subject: [PATCH net 0/2] tcp: fix congestion control UAFs in do_tcp_getsockopt() Date: Fri, 21 Aug 2026 14:24:47 -0400 Message-ID: <20260821182449.79785-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit do_tcp_getsockopt() has two lockless reads of icsk_ca_ops. Since BPF struct_ops congestion control made icsk_ca_ops point to dynamically allocated memory, a concurrent setsockopt(TCP_CONGESTION) can replace the pointer and free the old object while either reader is using it. Patch 1 fixes the TCP_CONGESTION path by copying ca_ops->name to a stack buffer while holding rcu_read_lock(). Patch 2 fixes the TCP_CC_INFO path by keeping the ca_ops->get_info lookup and call inside an RCU read-side critical section. Eric Dumazet's related TCP data-race annotation work [1] adds READ_ONCE()/WRITE_ONCE() annotations for lockless TCP socket field accesses. icsk_ca_ops would similarly benefit from such annotations, but that is an independent data-race concern. This series focuses solely on the use-after-free fixes via rcu_read_lock(). [1] https://lore.kernel.org/all/20260416200319.3608680-1-edumazet@google.com/ Cen Zhang (Microsoft) (2): tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO) net/ipv4/tcp.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) base-commit: 746fc0787f616da418ffc04a110296fe95d53491 -- 2.55.0