#syz test
From 51280720535aba38b63447c37229db102f276190 Mon Sep 17 00:00:00 2001
From: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx>
Date: Mon, 16 Dec 2024 13:39:42 +0800
Subject: [PATCH v2] exfat: fix the infinite loop in __exfat_free_cluster()
In __exfat_free_cluster(), the cluster chain is traversed until the
EOF cluster. If the cluster chain includes a loop due to file system
corruption, the EOF cluster cannot be traversed, resulting in an
infinite loop.
This commit uses the total number of clusters to prevent this infinite
loop.
Fixes: 31023864e67a ("exfat: add fat entry operations")
Signed-off-by: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx>
---
fs/exfat/fatent.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index 773c320d68f3..203c4dc2dce9 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -216,6 +216,16 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
if (err)
goto dec_used_clus;
+
+ if (num_clusters >= sbi->num_clusters - EXFAT_FIRST_CLUSTER) {
+ /*
+ * The cluster chain inlcudes a loop, scan the
+ * bitmap to get the number of used clusters.
+ */
+ exfat_count_used_clusters(sb, &sbi->used_clusters);
+
+ return 0;
+ }
} while (clu != EXFAT_EOF_CLUSTER);
}
--
2.43.0
