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 7DEF61C26 for ; Wed, 23 Nov 2022 09:02:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03FDBC433D6; Wed, 23 Nov 2022 09:02:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669194163; bh=J63EVeUd588ollkganXA5HrRwvMiTMwb76ZOMPs3eeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WMDoJCxr5TQXtMquLCyDY7ysT+U9sKfegecAcTOnDZgfwRvXW7L+gVFTdXcMv6m8u 50u3TMdxRoMudbNcnoHquJtjxbk56gkQq9KSKuMMW8tnrihvX7LNanZBeqKxN5nMdN I8gaKAWawsn/HD7n4mDW0HDNmfN7BfUvgdrXayvI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+dcf33a7aae997956fe06@syzkaller.appspotmail.com, Andrew Price , Andreas Gruenbacher Subject: [PATCH 4.14 82/88] gfs2: Check sb_bsize_shift after reading superblock Date: Wed, 23 Nov 2022 09:51:19 +0100 Message-Id: <20221123084551.520545806@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084548.535439312@linuxfoundation.org> References: <20221123084548.535439312@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Andrew Price commit 670f8ce56dd0632dc29a0322e188cc73ce3c6b92 upstream. Fuzzers like to scribble over sb_bsize_shift but in reality it's very unlikely that this field would be corrupted on its own. Nevertheless it should be checked to avoid the possibility of messy mount errors due to bad calculations. It's always a fixed value based on the block size so we can just check that it's the expected value. Tested with: mkfs.gfs2 -O -p lock_nolock /dev/vdb for i in 0 -1 64 65 32 33; do gfs2_edit -p sb field sb_bsize_shift $i /dev/vdb mount /dev/vdb /mnt/test && umount /mnt/test done Before this patch we get a withdraw after [ 76.413681] gfs2: fsid=loop0.0: fatal: invalid metadata block [ 76.413681] bh = 19 (type: exp=5, found=4) [ 76.413681] function = gfs2_meta_buffer, file = fs/gfs2/meta_io.c, line = 492 and with UBSAN configured we also get complaints like [ 76.373395] UBSAN: shift-out-of-bounds in fs/gfs2/ops_fstype.c:295:19 [ 76.373815] shift exponent 4294967287 is too large for 64-bit type 'long unsigned int' After the patch, these complaints don't appear, mount fails immediately and we get an explanation in dmesg. Reported-by: syzbot+dcf33a7aae997956fe06@syzkaller.appspotmail.com Signed-off-by: Andrew Price Signed-off-by: Andreas Gruenbacher Signed-off-by: Greg Kroah-Hartman --- fs/gfs2/ops_fstype.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -172,7 +172,10 @@ static int gfs2_check_sb(struct gfs2_sbd pr_warn("Invalid superblock size\n"); return -EINVAL; } - + if (sb->sb_bsize_shift != ffs(sb->sb_bsize) - 1) { + pr_warn("Invalid block size shift\n"); + return -EINVAL; + } return 0; }