From: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx> commit 03d9a9fe3f3aec508e485dd3dcfa1e99933b4bdb upstream. According to MS-CIFS specification MID 0xFFFF should not be used by the CIFS client, but we actually do. Besides, this has proven to cause races leading to oops between SendReceive2/cifs_demultiplex_thread. On SMB1, MID is a 2 byte value easy to reach in CurrentMid which may conflict with an oplock break notification request coming from server Signed-off-by: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx> Reviewed-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx> Reviewed-by: Aurelien Aptel <aaptel@xxxxxxxx> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx> CC: Stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/cifs/smb1ops.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/cifs/smb1ops.c +++ b/fs/cifs/smb1ops.c @@ -171,6 +171,9 @@ cifs_get_next_mid(struct TCP_Server_Info /* we do not want to loop forever */ last_mid = cur_mid; cur_mid++; + /* avoid 0xFFFF MID */ + if (cur_mid == 0xffff) + cur_mid++; /* * This nested loop looks more expensive than it is.
