linux-kernel - RE: drivers/vdpa/vdpa.c:296 vdpa_mgmtdev_fill() warn: should '(((1))) << (mdev->id

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Date:   Thu, 25 Nov 2021 17:39:42 +0000
From:   Parav Pandit <parav@...dia.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
CC:     "kbuild@...ts.01.org" <kbuild@...ts.01.org>,
        "lkp@...el.com" <lkp@...el.com>,
        "kbuild-all@...ts.01.org" <kbuild-all@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Eli Cohen <elic@...dia.com>, Jason Wang <jasowang@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: RE: drivers/vdpa/vdpa.c:296 vdpa_mgmtdev_fill() warn: should '(((1)))
 << (mdev->id_table[i]->device)' be a 64 bit type?



> From: Michael S. Tsirkin <mst@...hat.com>
> Sent: Thursday, November 25, 2021 9:46 PM
> 
> On Thu, Nov 25, 2021 at 10:03:28AM +0300, Dan Carpenter wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> master
> > head:   5d9f4cf36721aba199975a9be7863a3ff5cd4b59
> > commit: 33b347503f014ebf76257327cbc7001c6b721956 vdpa: Define vdpa
> > mgmt device, ops and a netlink interface
> > config: i386-randconfig-m021-20211118
> > (https://download.01.org/0day-
> ci/archive/20211125/202111250317.VUsGtdo
> > x-lkp@...el.com/config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> >
> > smatch warnings:
> > drivers/vdpa/vdpa.c:296 vdpa_mgmtdev_fill() warn: should '(((1))) << (mdev-
> >id_table[i]->device)' be a 64 bit type?
> >
> > vim +296 drivers/vdpa/vdpa.c
> >
> > 33b347503f014eb Parav Pandit 2021-01-05  280  static int
> vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *msg,
> > 33b347503f014eb Parav Pandit 2021-01-05  281  			     u32
> portid, u32 seq, int flags)
> > 33b347503f014eb Parav Pandit 2021-01-05  282  {
> > 33b347503f014eb Parav Pandit 2021-01-05  283  	u64
> supported_classes = 0;
> >                                                 ^^^^^^^^^^^^^^^^^^^^^
> > This is a u64
> >
> > 33b347503f014eb Parav Pandit 2021-01-05  284  	void *hdr;
> > 33b347503f014eb Parav Pandit 2021-01-05  285  	int i = 0;
> > 33b347503f014eb Parav Pandit 2021-01-05  286  	int err;
> > 33b347503f014eb Parav Pandit 2021-01-05  287
> > 33b347503f014eb Parav Pandit 2021-01-05  288  	hdr =
> genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags,
> VDPA_CMD_MGMTDEV_NEW);
> > 33b347503f014eb Parav Pandit 2021-01-05  289  	if (!hdr)
> > 33b347503f014eb Parav Pandit 2021-01-05  290  		return -
> EMSGSIZE;
> > 33b347503f014eb Parav Pandit 2021-01-05  291  	err =
> vdpa_nl_mgmtdev_handle_fill(msg, mdev);
> > 33b347503f014eb Parav Pandit 2021-01-05  292  	if (err)
> > 33b347503f014eb Parav Pandit 2021-01-05  293  		goto msg_err;
> > 33b347503f014eb Parav Pandit 2021-01-05  294
> > 33b347503f014eb Parav Pandit 2021-01-05  295  	while (mdev-
> >id_table[i].device) {
> > 33b347503f014eb Parav Pandit 2021-01-05 @296
> 	supported_classes |= BIT(mdev->id_table[i].device);
> >
> > Which suggests that this should be BIT_ULL().
> >
> > 33b347503f014eb Parav Pandit 2021-01-05  297  		i++;
> > 33b347503f014eb Parav Pandit 2021-01-05  298  	}
> > 33b347503f014eb Parav Pandit 2021-01-05  299
> > 33b347503f014eb Parav Pandit 2021-01-05  300  	if
> (nla_put_u64_64bit(msg, VDPA_ATTR_MGMTDEV_SUPPORTED_CLASSES,
> > 33b347503f014eb Parav Pandit 2021-01-05  301
> supported_classes, VDPA_ATTR_UNSPEC)) {
> > 33b347503f014eb Parav Pandit 2021-01-05  302  		err = -
> EMSGSIZE;
> > 33b347503f014eb Parav Pandit 2021-01-05  303  		goto msg_err;
> > 33b347503f014eb Parav Pandit 2021-01-05  304  	}
> > 33b347503f014eb Parav Pandit 2021-01-05  305
> > 33b347503f014eb Parav Pandit 2021-01-05  306  	genlmsg_end(msg,
> hdr);
> > 33b347503f014eb Parav Pandit 2021-01-05  307  	return 0;
> > 33b347503f014eb Parav Pandit 2021-01-05  308 33b347503f014eb Parav
> > Pandit 2021-01-05  309  msg_err:
> > 33b347503f014eb Parav Pandit 2021-01-05  310  	genlmsg_cancel(msg,
> hdr);
> > 33b347503f014eb Parav Pandit 2021-01-05  311  	return err;
> > 33b347503f014eb Parav Pandit 2021-01-05  312  }
> 
> 
> Parav? Any patches for this one?

Thanks Dan for reporting.

There are no in kernel drivers today that can register vdpa device with device id > 31.
But I agree that this code should not assume that.
I will shortly supply a patch to fix this warning.