[bug report] cifs: allow dumping keys for directories too

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Shyam Prasad N,

The patch 27bfeaa7b929: "cifs: allow dumping keys for directories
too" from Jun 16, 2023 (linux-next), leads to the following Smatch
static checker warning:

	fs/smb/client/ioctl.c:481 cifs_ioctl()
	error: 'tlink' dereferencing possible ERR_PTR()

fs/smb/client/ioctl.c
    469                 case CIFS_DUMP_FULL_KEY:
    470                         /*
    471                          * Dump encryption keys (handles any key sizes)
    472                          */
    473                         if (pSMBFile == NULL)
    474                                 break;
    475                         if (!capable(CAP_SYS_ADMIN)) {
    476                                 rc = -EACCES;
    477                                 break;
    478                         }
    479                         cifs_sb = CIFS_SB(inode->i_sb);
    480                         tlink = cifs_sb_tlink(cifs_sb);

cifs_sb_tlink() requires error checking.

--> 481                         tcon = tlink_tcon(tlink);
    482                         rc = cifs_dump_full_key(tcon, (void __user *)arg);
    483                         cifs_put_tlink(tlink);
    484                         break;
    485                 case CIFS_IOC_NOTIFY:
    486                         if (!S_ISDIR(inode->i_mode)) {
    487                                 /* Notify can only be done on directories */
    488                                 rc = -EOPNOTSUPP;
    489                                 break;
    490                         }
    491                         cifs_sb = CIFS_SB(inode->i_sb);
    492                         tlink = cifs_sb_tlink(cifs_sb);
    493                         if (IS_ERR(tlink)) {
    494                                 rc = PTR_ERR(tlink);
    495                                 break;
    496                         }
    497                         tcon = tlink_tcon(tlink);
    498                         if (tcon && tcon->ses->server->ops->notify) {
    499                                 rc = tcon->ses->server->ops->notify(xid,
    500                                                 filep, (void __user *)arg,
    501                                                 false /* no ret data */);
    502                                 cifs_dbg(FYI, "ioctl notify rc %d\n", rc);
    503                         } else
    504                                 rc = -EOPNOTSUPP;
    505                         cifs_put_tlink(tlink);
    506                         break;

regards,
dan carpenter