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Mon, 20 Apr 2026 19:51:32 -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 v2 1/2] Bluetooth: ISO: Fix data-race on dst in iso_sock_connect() Date: Tue, 21 Apr 2026 11:51:21 +0900 Message-ID: <20260421025122.55781-2-suunj1331@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260421025122.55781-1-suunj1331@gmail.com> References: <20260421025122.55781-1-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 reading the destination address directly from the local sockaddr argument (sa->iso_bdaddr) instead of iso_pi(sk)->dst. Since sa is a function-local argument, reading it requires no locking and avoids the race. 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index be145e2736b7..290a1b9a9daa 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -1193,7 +1193,7 @@ static int iso_sock_connect(struct socket *sock, struct sockaddr_unsized *addr, release_sock(sk); - if (bacmp(&iso_pi(sk)->dst, BDADDR_ANY)) + if (bacmp(&sa->iso_bdaddr, BDADDR_ANY)) err = iso_connect_cis(sk); else err = iso_connect_bis(sk); -- 2.52.0