SMB3: Fix crash in SMB2_open_init due to uninitialized field in compounding path

Ran into an intermittent crash in
SMB2_open_init+0x2f6/0x970
due to oparms.cifs_sb not being initialized when called from:
smb2_compound_op+0x45d/0x1690
Zero the whole oparms struct in the compounding path before setting up the
oparms so we don't risk any uninitialized fields.

Fixes: fdef665ba44a ("smb3: fix mode passed in on create for modetosid mount option")

Signed-off-by: Steve French <[e-mail]>
Acked-by: Ronnie Sahlberg <[e-mail]>
Reviewed-by: Pavel Shilovsky <[e-mail]>

fs/cifs/smb2inode.c

···
 		goto finished;
 	}
 
+	memset(&oparms, 0, sizeof(struct cifs_open_parms));
 	oparms.tcon = tcon;
 	oparms.desired_access = desired_access;
 	oparms.disposition = create_disposition;