Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Hoi Pok Wu <wuhoipok@gmail.com>
To:     shaggy@kernel.org
Cc:     Hoi Pok Wu <wuhoipok@gmail.com>,
        jfs-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org,
        syzbot+f0e0fcf3cd1047ae60ad@syzkaller.appspotmail.com,
        syzkaller-bugs@googlegroups.com
Subject: [PATCH V2] fs: jfs: fix shift-out-of-bounds in dbDiscardAG
Date:   Tue, 25 Oct 2022 23:20:45 +0800
Message-Id: <20221025152045.343650-1-wuhoipok@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@gmail.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