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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 F401FECDE30 for ; Wed, 17 Oct 2018 14:24:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C13D0205F4 for ; Wed, 17 Oct 2018 14:24:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C13D0205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727794AbeJQWUF (ORCPT ); Wed, 17 Oct 2018 18:20:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65397 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727013AbeJQWUE (ORCPT ); Wed, 17 Oct 2018 18:20:04 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DDF6F30001EF; Wed, 17 Oct 2018 14:24:08 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-250.rdu2.redhat.com [10.10.120.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7193E60150; Wed, 17 Oct 2018 14:23:59 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 4/4] fscache: Fix out of bound read in long cookie keys From: David Howells To: gregkh@linux-foundation.org Cc: syzbot+a95b989b2dde8e806af8@syzkaller.appspotmail.com, Eric Sandeen , viro@zeniv.linux.org.uk, sandeen@redhat.com, dhowells@redhat.com, linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 17 Oct 2018 15:23:59 +0100 Message-ID: <153978623918.8478.5800765927320866010.stgit@warthog.procyon.org.uk> In-Reply-To: <153978619457.8478.3813964117489247515.stgit@warthog.procyon.org.uk> References: <153978619457.8478.3813964117489247515.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 17 Oct 2018 14:24:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Sandeen fscache_set_key() can incur an out-of-bounds read, reported by KASAN: BUG: KASAN: slab-out-of-bounds in fscache_alloc_cookie+0x5b3/0x680 [fscache] Read of size 4 at addr ffff88084ff056d4 by task mount.nfs/32615 and also reported by syzbot at https://lkml.org/lkml/2018/7/8/236 BUG: KASAN: slab-out-of-bounds in fscache_set_key fs/fscache/cookie.c:120 [inline] BUG: KASAN: slab-out-of-bounds in fscache_alloc_cookie+0x7a9/0x880 fs/fscache/cookie.c:171 Read of size 4 at addr ffff8801d3cc8bb4 by task syz-executor907/4466 This happens for any index_key_len which is not divisible by 4 and is larger than the size of the inline key, because the code allocates exactly index_key_len for the key buffer, but the hashing loop is stepping through it 4 bytes (u32) at a time in the buf[] array. Fix this by calculating how many u32 buffers we'll need by using DIV_ROUND_UP, and then using kcalloc() to allocate a precleared allocation buffer to hold the index_key, then using that same count as the hashing index limit. Fixes: ec0328e46d6e ("fscache: Maintain a catalogue of allocated cookies") Reported-by: syzbot+a95b989b2dde8e806af8@syzkaller.appspotmail.com Signed-off-by: Eric Sandeen Signed-off-by: David Howells --- fs/fscache/cookie.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index b52f1dcd5dea..c550512ce335 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -70,7 +70,7 @@ void fscache_free_cookie(struct fscache_cookie *cookie) } /* - * Set the index key in a cookie. The cookie struct has space for a 12-byte + * Set the index key in a cookie. The cookie struct has space for a 16-byte * key plus length and hash, but if that's not big enough, it's instead a * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then * the key data. @@ -80,10 +80,13 @@ static int fscache_set_key(struct fscache_cookie *cookie, { unsigned long long h; u32 *buf; + int bufs; int i; + bufs = DIV_ROUND_UP(index_key_len, sizeof(*buf)); + if (index_key_len > sizeof(cookie->inline_key)) { - buf = kzalloc(index_key_len, GFP_KERNEL); + buf = kcalloc(bufs, sizeof(*buf), GFP_KERNEL); if (!buf) return -ENOMEM; cookie->key = buf; @@ -98,7 +101,8 @@ static int fscache_set_key(struct fscache_cookie *cookie, */ h = (unsigned long)cookie->parent; h += index_key_len + cookie->type; - for (i = 0; i < (index_key_len + sizeof(u32) - 1) / sizeof(u32); i++) + + for (i = 0; i < bufs; i++) h += buf[i]; cookie->key_hash = h ^ (h >> 32);