linux-kernel - [PATCH V2] fs: jfs: fix shift-out-of-bounds in dbDiscardAG

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Date:   Tue, 25 Oct 2022 23:20:45 +0800
From:   Hoi Pok Wu <wuhoipok@...il.com>
To:     shaggy@...nel.org
Cc:     Hoi Pok Wu <wuhoipok@...il.com>,
        jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+f0e0fcf3cd1047ae60ad@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com
Subject: [PATCH V2] fs: jfs: fix shift-out-of-bounds in dbDiscardAG

This should be applied to most URSAN bugs found recently by syzbot,
by guarding the dbMount. As syzbot feeding rubbish into the bmap
descriptor.

Signed-off-by: Hoi Pok Wu <wuhoipok@...il.com>
---
V1->2: guarding the corrupted data structure from dbMount instead
 fs/jfs/jfs_dmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index e1cbfbb60303..765838578a72 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -198,6 +198,11 @@ int dbMount(struct inode *ipbmap)
 		goto err_release_metapage;
 	}
 
+	if (((bmp->db_mapsize - 1) >> bmp->db_agl2size) > MAXAG) {
+		err = -EINVAL;
+		goto err_release_metapage;
+	}
+
 	for (i = 0; i < MAXAG; i++)
 		bmp->db_agfree[i] = le64_to_cpu(dbmp_le->dn_agfree[i]);
 	bmp->db_agsize = le64_to_cpu(dbmp_le->dn_agsize);
-- 
2.38.1