2022-01-04 15:13:18

by Jiasheng Jiang

Subject: [PATCH v2] virtio_ring: Check null pointer

As the alloc_indirect_packed() returns kmalloc_array() that could
allocation fail and return null pointer, it should be check in order to
prevent the dereference of null pointer.

Fixes: 1ce9e6055fa0 ("virtio_ring: introduce packed ring support")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
v2: Remove the redundant empty line.
---
drivers/virtio/virtio_ring.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 71e16b53e9c1..2923d8a68dc3 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -992,6 +992,10 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,

head = vq->packed.next_avail_idx;
desc = alloc_indirect_packed(total_sg, gfp);
+ if (!desc) {
+ END_USE(vq);
+ return -ENOMEM;
+ }

if (unlikely(vq->vq.num_free < 1)) {
pr_debug("Can't add buf len 1 - avail = 0\n");
--
2.25.1

2022-01-05 03:20:40

by Jason Wang

Subject: Re: [PATCH v2] virtio_ring: Check null pointer

On Tue, Jan 4, 2022 at 11:13 PM Jiasheng Jiang <[email protected]> wrote:
>
> As the alloc_indirect_packed() returns kmalloc_array() that could
> allocation fail and return null pointer, it should be check in order to
> prevent the dereference of null pointer.
>
> Fixes: 1ce9e6055fa0 ("virtio_ring: introduce packed ring support")
> Signed-off-by: Jiasheng Jiang <[email protected]>
> ---
> v2: Remove the redundant empty line.
> ---
> drivers/virtio/virtio_ring.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 71e16b53e9c1..2923d8a68dc3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -992,6 +992,10 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>
> head = vq->packed.next_avail_idx;
> desc = alloc_indirect_packed(total_sg, gfp);
> + if (!desc) {
> + END_USE(vq);
> + return -ENOMEM;

Just notice this:

My tree contains this commit: fc6d70f40b3d0 ("virtio_ring: check desc
== NULL when using indirect with packed"). It has fixed the wrong
error value but not the END_USE().

Thanks

> + }
>
> if (unlikely(vq->vq.num_free < 1)) {
> pr_debug("Can't add buf len 1 - avail = 0\n");
> --
> 2.25.1
>

2022-01-06 12:59:43

by Michael S. Tsirkin

Subject: Re: [PATCH v2] virtio_ring: Check null pointer

On Tue, Jan 04, 2022 at 11:12:51PM +0800, Jiasheng Jiang wrote:
> As the alloc_indirect_packed() returns kmalloc_array() that could
> allocation fail and return null pointer, it should be check in order to
> prevent the dereference of null pointer.
>
> Fixes: 1ce9e6055fa0 ("virtio_ring: introduce packed ring support")
> Signed-off-by: Jiasheng Jiang <[email protected]>


Well upstream has:

virtio_ring: check desc == NULL when using indirect with packed

so this no longer applies.
I think we do need to fix it: the END_USE is missing there.
Sending a patch.


> ---
> v2: Remove the redundant empty line.
> ---
> drivers/virtio/virtio_ring.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 71e16b53e9c1..2923d8a68dc3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -992,6 +992,10 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>
> head = vq->packed.next_avail_idx;
> desc = alloc_indirect_packed(total_sg, gfp);
> + if (!desc) {
> + END_USE(vq);
> + return -ENOMEM;
> + }
>
> if (unlikely(vq->vq.num_free < 1)) {
> pr_debug("Can't add buf len 1 - avail = 0\n");
> --
> 2.25.1