From d23f2621fc550127a2436012fea6124dabe8bbff Mon Sep 17 00:00:00 2001 From: Yuezhang Mo Date: Mon, 16 Dec 2024 13:39:42 +0800 Subject: [PATCH] exfat: fix the infinite loop in __exfat_free_cluster() [ Upstream commit a5324b3a488d883aa2d42f72260054e87d0940a0 ] 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. Reported-by: syzbot+1de5a37cb85a2d536330@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1de5a37cb85a2d536330 Tested-by: syzbot+1de5a37cb85a2d536330@syzkaller.appspotmail.com Fixes: 31023864e67a ("exfat: add fat entry operations") Signed-off-by: Yuezhang Mo Reviewed-by: Sungjong Seo Signed-off-by: Namjae Jeon Signed-off-by: Sasha Levin --- fs/exfat/fatent.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index 41ae4cce1f42..fe007ae2f23c 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 includes 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); }