smb: client: fix multiuser mount with krb5

Customer reported that they could no longer mount their SMB shares
with multiuser mount option and krb5.  Turned out that the client
wasn't duplicating username option when creating multiuser
connections, therefore failing to retrieve credentials as
cifs.upcall(8) couldn't find them in keytab.

Fix this by duplicating username option (if set) from original fs
context before creating multiuser connections with krb5.

Reproducer:

  ```
  $ ktutil
  ktutil:  add_entry -password -p testuser -k 1 -e aes256-cts
  Password for testuser@ZELDA.TEST:
  ktutil:  write_kt /etc/krb5.keytab
  ktutil:  quit
  $ klist -ke
  Keytab name: FILE:/etc/krb5.keytab
  KVNO Principal
   ---- ----------------------------------------------------------------
     1 testuser@ZELDA.TEST (aes256-cts-hmac-sha1-96)
  $ mount.cifs //w22-root2/scratch /mnt/1 -o \
      	uid=1000,sec=krb5,username=testuser@ZELDA.TEST,multiuser
  mount error(13): Permission denied
  Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) and
  kernel log messages (dmesg)
  ```

Reported-by: Jacob Shivers <jshivers@redhat.com>
Fixes: 12b4c5d98cd7 ("smb: client: fix krb5 mount with username option")
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

0 files changed, 0 insertions, 0 deletions