From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09106ECAAD5 for ; Tue, 6 Sep 2022 14:00:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240854AbiIFOA4 (ORCPT ); Tue, 6 Sep 2022 10:00:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240537AbiIFN5G (ORCPT ); Tue, 6 Sep 2022 09:57:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D888982D0D; Tue, 6 Sep 2022 06:42:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7A3036154A; Tue, 6 Sep 2022 13:41:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 856C6C433C1; Tue, 6 Sep 2022 13:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662471682; bh=/ku4iYcPiRQHqcXSV5f7lpnrnG969nJ6mcZXqPje1cM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Iwp9lkDaLkpZFXTYwoxJGyZCCzAB0csPmNBMjyIagP3abjOhfeCjENn90npKgYCDP 8+Zyq0Yetv0iX5Ayk6yjjE0QzNHKtKBOBviCiZzvsHbnkPlKuVNDtU/pelOZAlLOeP lhICht8vIMxsJX2xoBIiL33twbPU9jM9ESuHmxTQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, stable , Mazin Al Haddad , syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Subject: [PATCH 5.15 100/107] tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf() Date: Tue, 6 Sep 2022 15:31:21 +0200 Message-Id: <20220906132826.080174666@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220906132821.713989422@linuxfoundation.org> References: <20220906132821.713989422@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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->recieve 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") Cc: stable 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: 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 @@ -2753,7 +2753,8 @@ 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: