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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e6cae997csm3596214a91.11.2026.09.19.02.11.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 02:11:20 -0700 (PDT) From: Hui Peng To: Marcel Holtmann , Luiz Augusto von Dentz Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, Hui Peng Subject: [PATCH] Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO Date: Sat, 19 Sep 2026 09:11:20 +0000 Message-ID: <20260919091120.3273038-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The RFCOMM_CONNINFO getsockopt handler accepts a socket that is not connected as long as deferred setup is enabled: if (sk->sk_state != BT_CONNECTED && !rfcomm_pi(sk)->dlc->defer_setup) { err = -ENOTCONN; break; } l2cap_sk = rfcomm_pi(sk)->dlc->session->sock->sk; BT_DEFER_SETUP can be set on a listening socket, and it is stored in rfcomm_pi(sk)->dlc->defer_setup while dlc->session is still NULL. A local user can therefore create an RFCOMM socket, call listen(), set BT_DEFER_SETUP, and then call getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) to skip the -ENOTCONN path and dereference the NULL session: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002 KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 UID: 0 PID: 150 Comm: init Tainted: G B 7.3.0-rc3-g5dd1818b15d9 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:rfcomm_sock_getsockopt+0x529/0x780 Call Trace: do_sock_getsockopt+0x3ad/0x7d0 __sys_getsockopt+0x10e/0x1b0 __x64_sys_getsockopt+0xc2/0x160 do_syscall_64+0xda/0x4b0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Deferred setup only leaves a socket usable here once it has reached BT_CONNECT2, so restrict the exception to that state and check that a session is actually present before following it. Assisted-by: LLM Signed-off-by: Hui Peng --- No Fixes: tag: I could not pin the change that introduced this with confidence, so I left it out rather than guess. Reproduced on Linux 7.3.0-rc3 (5dd1818b15d9) with KASAN under QEMU with a virtual HCI device: s = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM); bind(s, ...); listen(s, 1); setsockopt(s, SOL_BLUETOOTH, BT_DEFER_SETUP, &one, 4); getsockopt(s, SOL_RFCOMM, RFCOMM_CONNINFO, &ci, &len); /* boom */ With this patch the getsockopt() returns -ENOTCONN instead. net/bluetooth/rfcomm/sock.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -786,8 +786,10 @@ static int rfcomm_sock_getsockopt_old(st break; case RFCOMM_CONNINFO: - if (sk->sk_state != BT_CONNECTED && - !rfcomm_pi(sk)->dlc->defer_setup) { + if ((sk->sk_state != BT_CONNECTED && + !(sk->sk_state == BT_CONNECT2 && + rfcomm_pi(sk)->dlc->defer_setup)) || + !rfcomm_pi(sk)->dlc->session) { err = -ENOTCONN; break; } -- 2.43.0