From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99DBE3074A4; Sat, 25 Oct 2025 16:23:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761409400; cv=none; b=tZSkXuF+gpunERWqsSDejgVHd8Rr/2fqTrCGGbaBg7hKyhicvLRekmmYIKS78zkPzPX2IV3JFQ025cSR8pDFW7hfxUJmPrcohDHczew7/tLjbwMJMGM2yLnB+gxjFcT+FIAwFgci6XGTCPvPJp2EaY2fyiD1EZ5GD05XCv4S/uI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761409400; c=relaxed/simple; bh=kvOgwdQrw973c1NxaZGdn6a9qg1RHHxO83UtbFKpj0s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=BFLjvjvfiLzRoHRSddyURyvLHh45zQdv49timIRuRhXepZMlcGodneaVJKeS7G7s160GAhDe+JvaZLlElpVaOEvX3Wt+8v8BHNj+o+fn8pFZxfM3a35gfk81rI8nDt0Q7KXG+XoLBpW6vbddfMsf2fwT2IRzawmSqQvSsBqmFXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=k/7MKA6f; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="k/7MKA6f" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78E11C4CEFF; Sat, 25 Oct 2025 16:23:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761409400; bh=kvOgwdQrw973c1NxaZGdn6a9qg1RHHxO83UtbFKpj0s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k/7MKA6fBJMJpjU0k3IL4rHozeNOwEaqZW0OMIfTp0TAj0wyXJGqw5q2XHDEq+sNO /ErRrFGFVCO75E/qfFAEBXYkQQnfMsmzi5++w936pP+ePz409ih8fJadZ8+YBqFzCi o97ZcNlXcHMe/kFMve9rmuB4tsXPdJijaaC6fqEU4tZHhEfayPlcZVriKJiiWOsRa3 iqS2G40CbMOr3m11+s3FTRu3EtUsOO8Rcl3/mdgIUIOyH3U7i2EGiYC3DADm1OlOcH 5Hu7X5zZFRaHKrF/iskP152qXcDcP6gb4m9y3U7ZAbJhhsUbwM+tpsOubES/AUUqH+ mHfCOPA1YHdDQ== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Ivan Pravdin , syzbot+4ed6852d4da4606c93da@syzkaller.appspotmail.com, Luiz Augusto von Dentz , Sasha Levin , marcel@holtmann.org, luiz.dentz@gmail.com, linux-bluetooth@vger.kernel.org Subject: [PATCH AUTOSEL 6.17-5.4] Bluetooth: bcsp: receive data only if registered Date: Sat, 25 Oct 2025 11:58:57 -0400 Message-ID: <20251025160905.3857885-306-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251025160905.3857885-1-sashal@kernel.org> References: <20251025160905.3857885-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.17.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Ivan Pravdin [ Upstream commit ca94b2b036c22556c3a66f1b80f490882deef7a6 ] Currently, bcsp_recv() can be called even when the BCSP protocol has not been registered. This leads to a NULL pointer dereference, as shown in the following stack trace: KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f] RIP: 0010:bcsp_recv+0x13d/0x1740 drivers/bluetooth/hci_bcsp.c:590 Call Trace: hci_uart_tty_receive+0x194/0x220 drivers/bluetooth/hci_ldisc.c:627 tiocsti+0x23c/0x2c0 drivers/tty/tty_io.c:2290 tty_ioctl+0x626/0xde0 drivers/tty/tty_io.c:2706 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f To prevent this, ensure that the HCI_UART_REGISTERED flag is set before processing received data. If the protocol is not registered, return -EUNATCH. Reported-by: syzbot+4ed6852d4da4606c93da@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=4ed6852d4da4606c93da Tested-by: syzbot+4ed6852d4da4606c93da@syzkaller.appspotmail.com Signed-off-by: Ivan Pravdin Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- LLM Generated explanations, may be completely bogus: YES – Guarding `bcsp_recv()` until the HCI UART core has successfully registered the driver prevents the real NULL-deref crash syzbot found, and the change is tiny, self-contained, and consistent with the rest of the UART transports. - `bcsp_complete_rx_pkt()` still hands completed frames to the core with `hci_recv_frame(hu->hdev, …)` (`drivers/bluetooth/hci_bcsp.c:562`), so if registration fails or has not finished, `hu->hdev` stays NULL and the dereference blows up exactly as in the reported stack trace. - The fix adds a single early `test_bit(HCI_UART_REGISTERED…)` gate (`drivers/bluetooth/hci_bcsp.c:585-586`). Returning `-EUNATCH` in this situation matches what the other UART transports already do (`drivers/bluetooth/hci_h4.c:112-113`, `drivers/bluetooth/hci_bcm.c:698-699`, etc.), so runtime behavior becomes consistent across protocols. - Callers ignore the return value and only bump stats when `hu->hdev` is valid (`drivers/bluetooth/hci_ldisc.c:618-631`), so refusing to process data before registration has no side effects beyond dropping input that could not be delivered anyway. - `HCI_UART_REGISTERED` is set only after `hci_register_dev()` succeeds (`drivers/bluetooth/hci_ldisc.c:691-699`) and is left clear when the registration path fails and `hu->hdev` is nulled (`drivers/bluetooth/hci_ldisc.c:693-695`), so the new guard precisely covers the hazardous window. - The change is minimal (two new lines), purely defensive, and fixes a syzbot-reported NULL dereference without touching protocol state machines or timing, making it an excellent candidate for stable backporting. drivers/bluetooth/hci_bcsp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/bluetooth/hci_bcsp.c b/drivers/bluetooth/hci_bcsp.c index 664d82d1e6139..591abe6d63ddb 100644 --- a/drivers/bluetooth/hci_bcsp.c +++ b/drivers/bluetooth/hci_bcsp.c @@ -582,6 +582,9 @@ static int bcsp_recv(struct hci_uart *hu, const void *data, int count) struct bcsp_struct *bcsp = hu->priv; const unsigned char *ptr; + if (!test_bit(HCI_UART_REGISTERED, &hu->flags)) + return -EUNATCH; + BT_DBG("hu %p count %d rx_state %d rx_count %ld", hu, count, bcsp->rx_state, bcsp->rx_count); -- 2.51.0