f2fs: check if file namelen exceeds max value

BugLink: https://bugs.launchpad.net/bugs/1892822

[ Upstream commit 720db068 ]

Dentry bitmap is not enough to detect incorrect dentries. So this patch
also checks the namelen value of a dentry.
Signed-off-by: Gong Chen <gongchen4@huawei.com>
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

fs/f2fs/dir.c

@@ -807,7 +807,8 @@ bool f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
 
 		/* check memory boundary before moving forward */
 		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
-		if (unlikely(bit_pos > d->max)) {
+		if (unlikely(bit_pos > d->max ||
+				le16_to_cpu(de->name_len) > F2FS_NAME_LEN)) {
 			f2fs_msg(F2FS_I_SB(d->inode)->sb, KERN_WARNING,
 				"%s: corrupted namelen=%d, run fsck to fix.",
 				__func__, le16_to_cpu(de->name_len));