cifs: use the correct max-length for dentry_path_raw()

RHBZ: 1972502

PATH_MAX is 4096 but PAGE_SIZE can be >4096 on some architectures
such as ppc and would thus write beyond the end of the actual object.

Cc: <[email protected]>
Reported-by: Xiaoli Feng <[email protected]>
Suggested-by: Brian foster <[email protected]>
Reviewed-by: Paulo Alcantara (SUSE) <[email protected]>
Signed-off-by: Ronnie Sahlberg <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: Ronnie Sahlberg

fs/cifs/dir.c

@@ -100,7 +100,7 @@ build_path_from_dentry_optional_prefix(struct dentry *direntry, void *page,
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
 		pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
 
-	s = dentry_path_raw(direntry, page, PAGE_SIZE);
+	s = dentry_path_raw(direntry, page, PATH_MAX);
 	if (IS_ERR(s))
 		return s;
 	if (!s[1])	// for root we want "", not "/"