linux-kernel - Forwarded: UBSAN: shift-out-of-bounds in dbAllocAG (3)

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Message-ID: <68f2a35a.050a0220.91a22.0429.GAE@google.com>
Date: Fri, 17 Oct 2025 13:13:14 -0700
From: syzbot <syzbot+4b717071f1eecb2972df@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Forwarded: UBSAN: shift-out-of-bounds in dbAllocAG (3)

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***

Subject: UBSAN: shift-out-of-bounds in dbAllocAG (3)
Author: hsukrut3@...il.com

#syz test
---
 fs/jfs/jfs_dmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cdfa699cd7c8..76f4b9322034 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1372,6 +1372,12 @@ dbAllocAG(struct bmap * bmp, int agno, s64 nblocks, int l2nb, s64 * results)
 	dcp = (struct dmapctl *) mp->data;
 	budmin = dcp->budmin;
 
+	if (unlikely(budmin < 0)) {
+		jfs_err("JFS: dmapctl corruption: budmin=%d", budmin);
+		release_metapage(mp);
+		return -EIO;
+	}
+
 	if (dcp->leafidx != cpu_to_le32(CTLLEAFIND)) {
 		jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmapctl page\n");
 		release_metapage(mp);
-- 
2.43.0