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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FB10C3A5A4 for ; Sun, 1 Sep 2019 14:34:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 31AB423429 for ; Sun, 1 Sep 2019 14:34:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567348467; bh=gk2OvUfPAWwW3W4/Jk9tCyRaDsCsDZb7stv3qVAQsRU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xHdfZDDJLhf3c6quWv++da0Uw9bcrcVhDM4tcjg8HkvlHldB37zh+JQpSGwWCD5DC uu+ZFIBIzABKYpYg+6ZZWDPv0ltvFHxWMvF5SUNytI3/g+TEAPodFzIVsc0NuUzm2f iD/DU/aDmqsTJNi79Ket6cIsRZlRqVAcbYPTnnOE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728908AbfIAOe0 (ORCPT ); Sun, 1 Sep 2019 10:34:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:54982 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726121AbfIAOeZ (ORCPT ); Sun, 1 Sep 2019 10:34:25 -0400 Received: from zzz.tds (h184-61-154-48.mdsnwi.dsl.dynamic.tds.net [184.61.154.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A943822CE9; Sun, 1 Sep 2019 14:34:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567348464; bh=gk2OvUfPAWwW3W4/Jk9tCyRaDsCsDZb7stv3qVAQsRU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ct4Q3SZPnhHtX+AWMMRBzvyD0bRoXD3TAtmpPG1Ly2yXp0FE4m9XU2/NMxIEjc6x4 mO3d16JZHSLfXLWkQZJ7LV+DNjV0pZ+Q3NF7c7qjxD0bd8KSDxlaHgVMdOT1BzK7Y9 asr7ZanemHbQboC16eprkS8kQMrbjeXf+fTdfVQY= From: Eric Biggers To: netdev@vger.kernel.org, "David S . Miller" Cc: Karsten Keil , syzkaller-bugs@googlegroups.com Subject: [PATCH net] isdn/capi: check message length in capi_write() Date: Sun, 1 Sep 2019 09:32:39 -0500 Message-Id: <20190901143239.13828-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <0000000000000e35f00581a579cd@google.com> References: <0000000000000e35f00581a579cd@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Biggers syzbot reported: BUG: KMSAN: uninit-value in capi_write+0x791/0xa90 drivers/isdn/capi/capi.c:700 CPU: 0 PID: 10025 Comm: syz-executor379 Not tainted 4.20.0-rc7+ #2 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x173/0x1d0 lib/dump_stack.c:113 kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:613 __msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313 capi_write+0x791/0xa90 drivers/isdn/capi/capi.c:700 do_loop_readv_writev fs/read_write.c:703 [inline] do_iter_write+0x83e/0xd80 fs/read_write.c:961 vfs_writev fs/read_write.c:1004 [inline] do_writev+0x397/0x840 fs/read_write.c:1039 __do_sys_writev fs/read_write.c:1112 [inline] __se_sys_writev+0x9b/0xb0 fs/read_write.c:1109 __x64_sys_writev+0x4a/0x70 fs/read_write.c:1109 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291 entry_SYSCALL_64_after_hwframe+0x63/0xe7 [...] The problem is that capi_write() is reading past the end of the message. Fix it by checking the message's length in the needed places. Reported-and-tested-by: syzbot+0849c524d9c634f5ae66@syzkaller.appspotmail.com Signed-off-by: Eric Biggers --- drivers/isdn/capi/capi.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c index 3c3ad42f22bf..a016d8c3c410 100644 --- a/drivers/isdn/capi/capi.c +++ b/drivers/isdn/capi/capi.c @@ -688,6 +688,9 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos if (!cdev->ap.applid) return -ENODEV; + if (count < CAPIMSG_BASELEN) + return -EINVAL; + skb = alloc_skb(count, GFP_USER); if (!skb) return -ENOMEM; @@ -698,7 +701,8 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos } mlen = CAPIMSG_LEN(skb->data); if (CAPIMSG_CMD(skb->data) == CAPI_DATA_B3_REQ) { - if ((size_t)(mlen + CAPIMSG_DATALEN(skb->data)) != count) { + if (count < 18 || + (size_t)(mlen + CAPIMSG_DATALEN(skb->data)) != count) { kfree_skb(skb); return -EINVAL; } @@ -711,6 +715,10 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos CAPIMSG_SETAPPID(skb->data, cdev->ap.applid); if (CAPIMSG_CMD(skb->data) == CAPI_DISCONNECT_B3_RESP) { + if (count < 12) { + kfree_skb(skb); + return -EINVAL; + } mutex_lock(&cdev->lock); capincci_free(cdev, CAPIMSG_NCCI(skb->data)); mutex_unlock(&cdev->lock); -- 2.23.0