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 CE8D737888; Mon, 18 Dec 2023 14:09:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="A1Dd91PE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5088BC433C8; Mon, 18 Dec 2023 14:09:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702908574; bh=va7HNli8k/oOFrgKty+EEZ40BqXlHHt3xvDsEG5wl+U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A1Dd91PEgslvJHfhHQRRgRgeG5qopEo8ZX1v+DHYk3aw0pzu9tttTBEs7Bnoc4g7W r3akW+Eq9fDKRPM/M+f81S6nxGOG3PAU/xcrm+OzS6A/GNU9cow65Mx5LAObIj0ynR oAkkhodC5zZbBxLfxi0DjOOndjI6T1OdgaFc3FLM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mazin Al Haddad , Gavrilov Ilia , syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Subject: [PATCH 5.10 60/62] tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf() Date: Mon, 18 Dec 2023 14:52:24 +0100 Message-ID: <20231218135048.826699791@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231218135046.178317233@linuxfoundation.org> References: <20231218135046.178317233@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mazin Al Haddad commit f16c6d2e58a4c2b972efcf9eb12390ee0ba3befb upstream A null pointer dereference can happen when attempting to access the "gsm->receive()" function in gsmld_receive_buf(). Currently, the code assumes that gsm->receive is only called after MUX activation. Since the gsmld_receive_buf() function can be accessed without the need to initialize the MUX, the gsm->receive() function will not be set and a NULL pointer dereference will occur. Fix this by avoiding the call to "gsm->receive()" in case the function is not initialized by adding a sanity check. Call Trace: gsmld_receive_buf+0x1c2/0x2f0 drivers/tty/n_gsm.c:2861 tiocsti drivers/tty/tty_io.c:2293 [inline] tty_ioctl+0xa75/0x15d0 drivers/tty/tty_io.c:2692 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Link: https://syzkaller.appspot.com/bug?id=bdf035c61447f8c6e0e6920315d577cb5cc35ac5 Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open") Reported-and-tested-by: syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Signed-off-by: Mazin Al Haddad Link: https://lore.kernel.org/r/20220814015211.84180-1-mazinalhaddad05@gmail.com Signed-off-by: Gavrilov Ilia Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2588,7 +2588,8 @@ static void gsmld_receive_buf(struct tty flags = *fp++; switch (flags) { case TTY_NORMAL: - gsm->receive(gsm, *cp); + if (gsm->receive) + gsm->receive(gsm, *cp); break; case TTY_OVERRUN: case TTY_BREAK: