[PATCH 2/2] cifs: Do not attempt to call CIFSGetSrvInodeNumber() without CAP_INFOLEVEL_PASSTHRU

["Pali Rohár" <pali@kernel.org>]

CIFSGetSrvInodeNumber() uses SMB_QUERY_FILE_INTERNAL_INFO (0x3ee) level
which is SMB PASSTHROUGH level (>= 0x03e8). SMB PASSTHROUGH levels are
supported only when server announce CAP_INFOLEVEL_PASSTHRU.

So add guard in cifs_query_file_info() function which is the only user of
CIFSGetSrvInodeNumber() function and returns -EOPNOTSUPP when server does
not announce CAP_INFOLEVEL_PASSTHRU.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 fs/smb/client/smb1ops.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index a0a15dda0949..d959097ec2d2 100644
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -622,7 +622,13 @@ static int cifs_get_srv_inum(const unsigned int xid, struct cifs_tcon *tcon,
 	 * There may be higher info levels that work but are there Windows
 	 * server or network appliances for which IndexNumber field is not
 	 * guaranteed unique?
+	 *
+	 * CIFSGetSrvInodeNumber() uses SMB_QUERY_FILE_INTERNAL_INFO
+	 * which is SMB PASSTHROUGH level therefore check for capability.
+	 * Note that this function can be called with tcon == NULL.
 	 */
+	if (tcon && !(tcon->ses->capabilities & CAP_INFOLEVEL_PASSTHRU))
+		return -EOPNOTSUPP;
 	return CIFSGetSrvInodeNumber(xid, tcon, full_path, uniqueid,
 				     cifs_sb->local_nls,
 				     cifs_remap(cifs_sb));
-- 
2.20.1