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([147.46.174.222]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c164f85de1sm101060345ad.20.2026.06.05.14.48.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jun 2026 14:48:10 -0700 (PDT) From: Sechang Lim To: John Fastabend , Jakub Kicinski , Sabrina Dubroca , "David S . Miller" , Eric Dumazet , Paolo Abeni Cc: Simon Horman , Jiayuan Chen , Alexei Starovoitov , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net] tls: fix use-after-free in tls_sw_sendmsg() cork error path Date: Fri, 5 Jun 2026 21:48:00 +0000 Message-ID: <20260605214802.1647008-1-rhkrqnwk98@gmail.com> X-Mailer: git-send-email 2.43.0 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" tls_sw_sendmsg_locked() caches a pointer into the open record: rec =3D ctx->open_rec; msg_pl =3D &rec->msg_plaintext; and keeps using msg_pl after bpf_exec_tx_verdict(). When an attached SK_MSG bpf program calls bpf_msg_apply_bytes(), tls_push_record() splits the open record: the original record is encrypted, queued and freed by tls_tx_records(), while ctx->open_rec is replaced by the split remainder. If the bpf program also sets cork_bytes, bpf_exec_tx_verdict() then returns -ENOSPC, and the error path dereferences the now-dangling msg_pl: else if (ctx->open_rec && ret =3D=3D -ENOSPC) { if (msg_pl->cork_bytes) { /* use-after-free */ BUG: KASAN: slab-use-after-free in tls_sw_sendmsg+0x118d/0x16f0 Read of size 4 at addr ffff88810a36f2ac by task syz.0.17/2056 CPU: 1 UID: 0 PID: 2056 Comm: syz.0.17 Not tainted 7.1.0-rc6 #2 Call Trace: tls_sw_sendmsg+0x118d/0x16f0 __sock_sendmsg+0xe4/0x130 __sys_sendto+0x2fe/0x3f0 __x64_sys_sendto+0x7b/0x90 do_syscall_64+0x14c/0x480 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 2056: tls_get_rec+0x7a/0x3d0 tls_sw_sendmsg+0x3cd/0x16f0 __sock_sendmsg+0xe4/0x130 __sys_sendto+0x2fe/0x3f0 Freed by task 2056: kfree+0x163/0x560 tls_tx_records+0x2d6/0x380 bpf_exec_tx_verdict+0x3de/0xd50 tls_sw_sendmsg+0x10e9/0x16f0 __sock_sendmsg+0xe4/0x130 __sys_sendto+0x2fe/0x3f0 ctx->open_rec already points at the live record on this path, so re-fetch msg_pl from it before use. Fixes: 54a3ecaeeeae ("bpf: fix ktls panic with sockmap") Signed-off-by: Sechang Lim --- net/tls/tls_sw.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index 964ebc268ee4..39dee66cc99b 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -1165,6 +1165,7 @@ static int tls_sw_sendmsg_locked(struct sock *sk, str= uct msghdr *msg, else if (ret =3D=3D -ENOMEM) goto wait_for_memory; else if (ctx->open_rec && ret =3D=3D -ENOSPC) { + msg_pl =3D &ctx->open_rec->msg_plaintext; if (msg_pl->cork_bytes) { ret =3D 0; goto send_end; --=20 2.43.0