From 2cc7cc01c15f57d056318c33705647f87dcd4aab Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@gmail.com>
Date: Sat, 19 Mar 2022 22:30:00 +0300
Subject: [PATCH] jfs: fix divide error in dbNextAG
Git-commit: 2cc7cc01c15f57d056318c33705647f87dcd4aab
Patch-mainline: v5.18-rc1
References: bsc#1200828
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>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/jfs/jfs_dmap.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 91f4ec93dab1..d8502f4989d9 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -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);
--
2.35.3