[PATCH 05/12] cifs: Fix cifs_query_path_info() for Windows NT servers

["Pali Rohár" <pali@kernel.org>]

For TRANS2 QUERY_PATH_INFO request when the path does not exist, the
Windows NT SMB server returns error response STATUS_OBJECT_NAME_NOT_FOUND
or ERRDOS/ERRbadfile without the SMBFLG_RESPONSE flag set. Similarly it
returns STATUS_DELETE_PENDING when the file is being deleted. And looks
like that any error response from TRANS2 QUERY_PATH_INFO does not have
SMBFLG_RESPONSE flag set.

So relax check in check_smb_hdr() for detecting if the packet is response
for this special case.

This change fixes stat() operation against Windows NT SMB servers and also
all operations which depends on -ENOENT result from stat like creat() or
mkdir().

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 fs/smb/client/misc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c
index 4373dd64b66d..5122f3895dfc 100644
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -323,6 +323,14 @@ check_smb_hdr(struct smb_hdr *smb)
 	if (smb->Command == SMB_COM_LOCKING_ANDX)
 		return 0;
 
+	/*
+	 * Windows NT server returns error resposne (e.g. STATUS_DELETE_PENDING
+	 * or STATUS_OBJECT_NAME_NOT_FOUND or ERRDOS/ERRbadfile or any other)
+	 * for some TRANS2 requests without the RESPONSE flag set in header.
+	 */
+	if (smb->Command == SMB_COM_TRANSACTION2 && smb->Status.CifsError != 0)
+		return 0;
+
 	cifs_dbg(VFS, "Server sent request, not response. mid=%u\n",
 		 get_mid(smb));
 	return 1;
-- 
2.20.1