linux-kernel - [PATCH AUTOSEL 5.10 04/16] fs/jfs: Add check for negative db

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Date:   Tue,  7 Nov 2023 10:52:23 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Juntong Deng <juntong.deng@...look.com>,
        syzbot+debee9ab7ae2b34b0307@...kaller.appspotmail.com,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Sasha Levin <sashal@...nel.org>, shaggy@...nel.org,
        wonguk.lee1023@...il.com, liushixin2@...wei.com,
        andrew.kanner@...il.com, yogi.kernel@...il.com,
        ghandatmanas@...il.com, code@...dh.me,
        jfs-discussion@...ts.sourceforge.net
Subject: [PATCH AUTOSEL 5.10 04/16] fs/jfs: Add check for negative db_l2nbperpage

From: Juntong Deng <juntong.deng@...look.com>

[ Upstream commit 525b861a008143048535011f3816d407940f4bfa ]

l2nbperpage is log2(number of blks per page), and the minimum legal
value should be 0, not negative.

In the case of l2nbperpage being negative, an error will occur
when subsequently used as shift exponent.

Syzbot reported this bug:

UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:799:12
shift exponent -16777216 is negative

Reported-by: syzbot+debee9ab7ae2b34b0307@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=debee9ab7ae2b34b0307
Signed-off-by: Juntong Deng <juntong.deng@...look.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/jfs/jfs_dmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a9c078fc2302a..06dda2c7a6e24 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -180,7 +180,8 @@ 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);
-	if (bmp->db_l2nbperpage > L2PSIZE - L2MINBLOCKSIZE) {
+	if (bmp->db_l2nbperpage > L2PSIZE - L2MINBLOCKSIZE ||
+		bmp->db_l2nbperpage < 0) {
 		err = -EINVAL;
 		goto err_release_metapage;
 	}
-- 
2.42.0