linux-kernel - Syzbot testing for v3: ocfs2: fix kernel BUG in ocfs2_find_victim

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Message-Id: <20251201121703.128667-1-activprithvi@gmail.com>
Date: Mon,  1 Dec 2025 17:47:03 +0530
From: Prithvi Tambewagh <activprithvi@...il.com>
To: syzbot+96d38c6e1655c1420a72@...kaller.appspotmail.com,
	jlbec@...lplan.org,
	joseph.qi@...ux.alibaba.com,
	mark@...heh.com
Cc: linux-kernel@...r.kernel.org,
	ocfs2-devel@...ts.linux.dev,
	syzkaller-bugs@...glegroups.com,
	Prithvi Tambewagh <activprithvi@...il.com>
Subject: Syzbot testing for v3: ocfs2: fix kernel BUG in ocfs2_find_victim_chain

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 939f15e640f193616691d3bcde0089760e75b0d3

Signed-off-by: Prithvi Tambewagh <activprithvi@...il.com>
---
 fs/ocfs2/suballoc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index 6ac4dcd54588..e93fc842bb20 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -1992,6 +1992,16 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
 	}
 
 	cl = (struct ocfs2_chain_list *) &fe->id2.i_chain;
+	if (!le16_to_cpu(cl->cl_next_free_rec) ||
+	    le16_to_cpu(cl->cl_next_free_rec) > le16_to_cpu(cl->cl_count)) {
+		status = ocfs2_error(ac->ac_inode->i_sb,
+				     "Chain allocator dinode %llu has invalid next "
+				     "free chain record %u, but only %u total\n",
+				     (unsigned long long)le64_to_cpu(fe->i_blkno),
+				     le16_to_cpu(cl->cl_next_free_rec),
+				     le16_to_cpu(cl->cl_count));
+		goto bail;
+	}
 
 	victim = ocfs2_find_victim_chain(cl);
 	ac->ac_chain = victim;

base-commit: 939f15e640f193616691d3bcde0089760e75b0d3
-- 
2.34.1