linux-kernel - [PATCH] jfs: fix oob in dbFindLeaf

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Message-ID: <tencent_5E4F8F8DEFA5930D909222DDE35DCE192A07@qq.com>
Date: Thu,  8 Jan 2026 22:45:44 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+1afe7ef2d0062e19eeb3@...kaller.appspotmail.com
Cc: jfs-discussion@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	shaggy@...nel.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] jfs: fix oob in dbFindLeaf

The initial value of x is ti, and there is a potential risk that the
value of ti might equal max_size.  The existing boundary checks have
been improved to prevent the out-of-bounds (OOB) issue [1] reported
by syzbot.

[1]
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:2976:16
index 1365 is out of range for type 's8[1365]' (aka 'signed char[1365]')
Call Trace:
 dbFindLeaf+0x308/0x520 fs/jfs/jfs_dmap.c:2976
 dbFindCtl+0x267/0x520 fs/jfs/jfs_dmap.c:1717
 dbAllocAny fs/jfs/jfs_dmap.c:1527 [inline]

Reported-by: syzbot+1afe7ef2d0062e19eeb3@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1afe7ef2d0062e19eeb3
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/jfs/jfs_dmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cdfa699cd7c8..18a7dc58f289 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2971,7 +2971,7 @@ static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
 			/* sufficient free space found.  move to the next
 			 * level (or quit if this is the last level).
 			 */
-			if (x + n > max_size)
+			if (x + n >= max_size)
 				return -ENOSPC;
 			if (l2nb <= tp->dmt_stree[x + n])
 				break;
-- 
2.43.0