Commit cec71a71 authored Mar 19, 2022 by Pavel Skripkin Committed by Greg Kroah-Hartman Apr 15, 2022

jfs: fix divide error in dbNextAG



[ Upstream commit 2cc7cc01c15f57d056318c33705647f87dcd4aab ]

Syzbot reported divide error in dbNextAG(). The problem was in missing
validation check for malicious image.

Syzbot crafted an image with bmp->db_numag equal to 0. There wasn't any
validation checks, but dbNextAG() blindly use bmp->db_numag in divide
expression

Fix it by validating bmp->db_numag in dbMount() and return an error if
image is malicious

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reported-and-tested-by:  <syzbot+46f5c25af73eb8330eb6@syzkaller.appspotmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent b3ac1e01

fs/jfs/jfs_dmap.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -148,6 +148,7 @@ static const s8 budtab[256] = {
		* 0 - success
		* -ENOMEM - insufficient memory
		* -EIO - i/o error
		* -EINVAL - wrong bmap data
		*/
		int dbMount(struct inode *ipbmap)
		{
		@@ -179,6 +180,12 @@ int dbMount(struct inode *ipbmap)
		bmp->db_nfree = le64_to_cpu(dbmp_le->dn_nfree);
		bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
		bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
		if (!bmp->db_numag) {
		release_metapage(mp);
		kfree(bmp);
		return -EINVAL;
		}

		bmp->db_maxlevel = le32_to_cpu(dbmp_le->dn_maxlevel);
		bmp->db_maxag = le32_to_cpu(dbmp_le->dn_maxag);
		bmp->db_agpref = le32_to_cpu(dbmp_le->dn_agpref);