6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Namjae Jeon [ Upstream commit 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95 ] ksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path resolution within the share root. When a crafted path attempts to escape the share boundary using parent-directory components ('..'), vfs_path_parent_lookup() detects this and immediately fails, returning -EXDEV. However, a bug exists in __ksmbd_vfs_kern_path() under caseless mode. The function fails to intercept the -EXDEV error and erroneously falls through to the caseless retry logic, which is intended only for genuinely missing files. During this retry process, the path is reconstructed, leading to an unintended LOOKUP_BENEATH bypass that allows write-capable users to create zero-length files or directories outside the exported share. Fix this by ensuring that the execution only proceeds to the caseless lookup retry when the error is specifically -ENOENT. Any other errors, such as -EXDEV from a path traversal attempt, must be returned immediately. Cc: stable@vger.kernel.org Reported-by: Y s65 Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/server/vfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c index ec9d04e4de416..3ac5f3f48121d 100644 --- a/fs/smb/server/vfs.c +++ b/fs/smb/server/vfs.c @@ -1238,7 +1238,7 @@ int __ksmbd_vfs_kern_path(struct ksmbd_work *work, char *filepath, retry: err = ksmbd_vfs_path_lookup(share_conf, filepath, flags, path, do_lock); - if (!err || !caseless) + if (!err || err != -ENOENT || !caseless) return err; path_len = strlen(filepath); -- 2.53.0