RE: [PATCH] virtio_pci: fix a NULL pointer reference in vp_del_vqs

[Gonglei (Arei)]

> -----Original Message-----
> From: longpeng
> Sent: Saturday, March 09, 2019 3:18 PM
> To: mst@xxxxxxxxxx; jasowang@xxxxxxxxxx
> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> longpeng <longpeng2@xxxxxxxxxx>; Gonglei (Arei)
> <arei.gonglei@xxxxxxxxxx>
> Subject: [PATCH] virtio_pci: fix a NULL pointer reference in vp_del_vqs
> 
> From: Longpeng <longpeng2@xxxxxxxxxx>
> 
> If the msix_affinity_masks is alloced failed, then we'll
> try to free some resources in vp_free_vectors() that may
> access it directly.
> 
> We met the following stack in our production:
> [   29.296767] BUG: unable to handle kernel NULL pointer dereference at
> (null)
> [   29.311151] IP: [<ffffffffc04fe35a>] vp_free_vectors+0x6a/0x150 [virtio_pci]
> [   29.324787] PGD 0
> [   29.333224] Oops: 0000 [#1] SMP
> [...]
> [   29.425175] RIP: 0010:[<ffffffffc04fe35a>]  [<ffffffffc04fe35a>]
> vp_free_vectors+0x6a/0x150 [virtio_pci]
> [   29.441405] RSP: 0018:ffff9a55c2dcfa10  EFLAGS: 00010206
> [   29.453491] RAX: 0000000000000000 RBX: ffff9a55c322c400 RCX:
> 0000000000000000
> [   29.467488] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
> ffff9a55c322c400
> [   29.481461] RBP: ffff9a55c2dcfa20 R08: 0000000000000000 R09:
> ffffc1b6806ff020
> [   29.495427] R10: 0000000000000e95 R11: 0000000000aaaaaa R12:
> 0000000000000000
> [   29.509414] R13: 0000000000010000 R14: ffff9a55bd2d9e98 R15:
> ffff9a55c322c400
> [   29.523407] FS:  00007fdcba69f8c0(0000) GS:ffff9a55c2840000(0000)
> knlGS:0000000000000000
> [   29.538472] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   29.551621] CR2: 0000000000000000 CR3: 000000003ce52000 CR4:
> 00000000003607a0
> [   29.565886] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [   29.580055] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400
> [   29.594122] Call Trace:
> [   29.603446]  [<ffffffffc04fe8a2>] vp_request_msix_vectors+0xe2/0x260
> [virtio_pci]
> [   29.618017]  [<ffffffffc04fedc5>] vp_try_to_find_vqs+0x95/0x3b0
> [virtio_pci]
> [   29.632152]  [<ffffffffc04ff117>] vp_find_vqs+0x37/0xb0 [virtio_pci]
> [   29.645582]  [<ffffffffc057bf63>] init_vq+0x153/0x260 [virtio_blk]
> [   29.658831]  [<ffffffffc057c1e8>] virtblk_probe+0xe8/0x87f [virtio_blk]
> [...]
> 
> Cc: Gonglei <arei.gonglei@xxxxxxxxxx>
> Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
> ---
>  drivers/virtio/virtio_pci_common.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 

Reviewed-by: Gonglei <arei.gonglei@xxxxxxxxxx>

Thanks,
-Gonglei

> diff --git a/drivers/virtio/virtio_pci_common.c
> b/drivers/virtio/virtio_pci_common.c
> index d0584c0..7a0398b 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -255,9 +255,11 @@ void vp_del_vqs(struct virtio_device *vdev)
>  	for (i = 0; i < vp_dev->msix_used_vectors; ++i)
>  		free_irq(pci_irq_vector(vp_dev->pci_dev, i), vp_dev);
> 
> -	for (i = 0; i < vp_dev->msix_vectors; i++)
> -		if (vp_dev->msix_affinity_masks[i])
> -			free_cpumask_var(vp_dev->msix_affinity_masks[i]);
> +	if (vp_dev->msix_affinity_masks) {
> +		for (i = 0; i < vp_dev->msix_vectors; i++)
> +			if (vp_dev->msix_affinity_masks[i])
> +				free_cpumask_var(vp_dev->msix_affinity_masks[i]);
> +	}
> 
>  	if (vp_dev->msix_enabled) {
>  		/* Disable the vector used for configuration */
> --
> 1.8.3.1
>