diff mbox series

[4.19,179/338] jfs: fix divide error in dbNextAG

Message ID 20220414110843.993017879@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH April 14, 2022, 1:11 p.m. UTC 
From: Pavel Skripkin <paskripkin@gmail.com>

[ 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: 1da177e4c3f4 ("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>
---
 fs/jfs/jfs_dmap.c | 7 +++++++
 1 file changed, 7 insertions(+)
diff mbox series

Patch

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 687b07b9b4f6..f05805a10a50 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -161,6 +161,7 @@  static const s8 budtab[256] = {
  *	0	- success
  *	-ENOMEM	- insufficient memory
  *	-EIO	- i/o error
+ *	-EINVAL - wrong bmap data
  */
 int dbMount(struct inode *ipbmap)
 {
@@ -192,6 +193,12 @@  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);