6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx> [ 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@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=1de5a37cb85a2d536330 Tested-by: syzbot+1de5a37cb85a2d536330@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 31023864e67a ("exfat: add fat entry operations") Signed-off-by: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx> Reviewed-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx> Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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); } -- 2.39.5
