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Fri, 17 Apr 2026 22:34:24 -0700 (PDT) From: SeungJu Cheon To: luiz.dentz@gmail.com, marcel@holtmann.org Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, me@brighamcampbell.com, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linux.dev, SeungJu Cheon Subject: [PATCH 1/2] Bluetooth: ISO: Fix data-race on dst in iso_sock_connect() Date: Sat, 18 Apr 2026 14:34:00 +0900 Message-ID: <20260418053401.128483-2-suunj1331@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260418053401.128483-1-suunj1331@gmail.com> References: <20260418053401.128483-1-suunj1331@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit iso_sock_connect() copies the destination address into iso_pi(sk)->dst under lock_sock, then releases the lock and reads it back with bacmp() to decide between the CIS and BIS connect paths: lock_sock(sk); bacpy(&iso_pi(sk)->dst, &sa->iso_bdaddr); iso_pi(sk)->dst_type = sa->iso_bdaddr_type; release_sock(sk); if (bacmp(&iso_pi(sk)->dst, BDADDR_ANY)) // <- no lock held This read after release_sock() races with any concurrent write to iso_pi(sk)->dst on the same socket. Fix by performing the bacmp() inside the lock_sock critical section and caching the result in a local variable. This patch addresses only the bacmp() race in iso_sock_connect(); other unprotected iso_pi(sk) accesses are fixed separately in the next patch. KCSAN report: BUG: KCSAN: data-race in memcmp+0x39/0xb0 race at unknown origin, with read to 0xffff8f96ea66dde3 of 1 bytes by task 549 on cpu 1: memcmp+0x39/0xb0 iso_sock_connect+0x275/0xb40 __sys_connect_file+0xbd/0xe0 __sys_connect+0xe0/0x110 __x64_sys_connect+0x40/0x50 x64_sys_call+0xcad/0x1c60 do_syscall_64+0x133/0x590 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00 -> 0xee Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 549 Comm: iso_race_combin Not tainted 7.0.0-08391-g1d51b370a0f8 #40 PREEMPT(lazy) Fixes: ccf74f2390d6 ("Bluetooth: Add BTPROTO_ISO socket type") Signed-off-by: SeungJu Cheon --- net/bluetooth/iso.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index be145e2736b7..14963ba68597 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -1169,6 +1169,7 @@ static int iso_sock_connect(struct socket *sock, struct sockaddr_unsized *addr, struct sockaddr_iso *sa = (struct sockaddr_iso *)addr; struct sock *sk = sock->sk; int err; + bool bcast; BT_DBG("sk %p", sk); @@ -1191,9 +1192,11 @@ static int iso_sock_connect(struct socket *sock, struct sockaddr_unsized *addr, bacpy(&iso_pi(sk)->dst, &sa->iso_bdaddr); iso_pi(sk)->dst_type = sa->iso_bdaddr_type; + bcast = !bacmp(&iso_pi(sk)->dst, BDADDR_ANY); + release_sock(sk); - if (bacmp(&iso_pi(sk)->dst, BDADDR_ANY)) + if (!bcast) err = iso_connect_cis(sk); else err = iso_connect_bis(sk); -- 2.52.0