From 6bacc0789fc947e24e675b520e0b8fbd0e694846 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() BugLink: https://bugs.launchpad.net/bugs/2106770 [ 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 Signed-off-by: Manuel Diewald Signed-off-by: Mehmet Basaran --- fs/exfat/fatent.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index 56b870d9cc0d..428d862a1d2b 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); }