cifs: Add minor debug message during negprot

Check for unknown security mode flags during negotiate protocol
if debugging enabled.

Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

2 files changed, 5 insertions, 1 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 0e04b577758d..f7741cee2a4c 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -584,8 +584,10 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
                                SMB2_MAX_BUFFER_SIZE);
         server->max_read = le32_to_cpu(rsp->MaxReadSize);
         server->max_write = le32_to_cpu(rsp->MaxWriteSize);
-        /* BB Do we need to validate the SecurityMode? */
         server->sec_mode = le16_to_cpu(rsp->SecurityMode);
+        if ((server->sec_mode & SMB2_SEC_MODE_FLAGS_ALL) != server->sec_mode)
+                cifs_dbg(FYI, "Server returned unexpected security mode 0x%x\n",
+                                server->sec_mode);
         server->capabilities = le32_to_cpu(rsp->Capabilities);
         /* Internal types */
         server->capabilities |= SMB2_NT_FIND | SMB2_LARGE_FILES;
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 8b901c69a65a..253e2c7c952f 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -249,6 +249,8 @@ struct smb2_negotiate_req {
 /* SecurityMode flags */
 #define SMB2_NEGOTIATE_SIGNING_ENABLED  0x0001
 #define SMB2_NEGOTIATE_SIGNING_REQUIRED 0x0002
+#define SMB2_SEC_MODE_FLAGS_ALL         0x0003
+
 /* Capabilities flags */
 #define SMB2_GLOBAL_CAP_DFS             0x00000001
 #define SMB2_GLOBAL_CAP_LEASING         0x00000002 /* Resp only New to SMB2.1 */