[CIFS] When mandatory encryption on share, fail mount

    When mandatory encryption is configured in samba server on a
    share (smb.conf parameter "smb encrypt = mandatory") the
    server will hang up the tcp session when we try to send
    the first frame after the tree connect if it is not a
    QueryFSUnixInfo, this causes cifs mount to hang (it must
    be killed with ctl-c).  Move the QueryFSUnixInfo call
    earlier in the mount sequence, and check whether the SetFSUnixInfo
    fails due to mandatory encryption so we can return a sensible
    error (EACCES) on mount.

    In a future patch (for 2.6.40) we will support mandatory
    encryption.

CC: Stable <stable@kernel.org>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/connect.c

@@ -2530,7 +2530,7 @@ void reset_cifs_unix_caps(int xid, struct cifsTconInfo *tcon,
 
 	if (!CIFSSMBQFSUnixInfo(xid, tcon)) {
 		__u64 cap = le64_to_cpu(tcon->fsUnixInfo.Capability);
-
+		cFYI(1, "unix caps which server supports %lld", cap);
 		/* check for reconnect case in which we do not
 		   want to change the mount behavior if we can avoid it */
 		if (vol_info == NULL) {
@@ -2548,6 +2548,9 @@ void reset_cifs_unix_caps(int xid, struct cifsTconInfo *tcon,
 			}
 		}
 
+		if (cap & CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP)
+			cERROR(1, "per-share encryption not supported yet");
+
 		cap &= CIFS_UNIX_CAP_MASK;
 		if (vol_info && vol_info->no_psx_acl)
 			cap &= ~CIFS_UNIX_POSIX_ACL_CAP;
@@ -2596,6 +2599,10 @@ void reset_cifs_unix_caps(int xid, struct cifsTconInfo *tcon,
 			cFYI(1, "very large read cap");
 		if (cap & CIFS_UNIX_LARGE_WRITE_CAP)
 			cFYI(1, "very large write cap");
+		if (cap & CIFS_UNIX_TRANSPORT_ENCRYPTION_CAP)
+			cFYI(1, "transport encryption cap");
+		if (cap & CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP)
+			cFYI(1, "mandatory transport encryption cap");
 #endif /* CIFS_DEBUG2 */
 		if (CIFSSMBSetFSUnixInfo(xid, tcon, cap)) {
 			if (vol_info == NULL) {
@@ -3022,20 +3029,26 @@ try_mount_again:
 		goto remote_path_check;
 	}
 
-	/* do not care if following two calls succeed - informational */
-	if (!tcon->ipc) {
-		CIFSSMBQFSDeviceInfo(xid, tcon);
-		CIFSSMBQFSAttributeInfo(xid, tcon);
-	}
-
 	/* tell server which Unix caps we support */
-	if (tcon->ses->capabilities & CAP_UNIX)
+	if (tcon->ses->capabilities & CAP_UNIX) {
 		/* reset of caps checks mount to see if unix extensions
 		   disabled for just this mount */
 		reset_cifs_unix_caps(xid, tcon, sb, volume_info);
-	else
+		if ((tcon->ses->server->tcpStatus == CifsNeedReconnect) &&
+		    (le64_to_cpu(tcon->fsUnixInfo.Capability) &
+		     CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP)) {
+			rc = -EACCES;
+			goto mount_fail_check;
+		}
+	} else
 		tcon->unix_ext = 0; /* server does not support them */
 
+	/* do not care if following two calls succeed - informational */
+	if (!tcon->ipc) {
+		CIFSSMBQFSDeviceInfo(xid, tcon);
+		CIFSSMBQFSAttributeInfo(xid, tcon);
+	}
+
 	/* convert forward to back slashes in prepath here if needed */
 	if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) == 0)
 		convert_delimiter(cifs_sb->prepath, CIFS_DIR_SEP(cifs_sb));