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Message-ID: <20210517193641-mutt-send-email-mst@kernel.org>
Date: Mon, 17 May 2021 19:39:02 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Xie Yongji <xieyongji@...edance.com>
Cc: jasowang@...hat.com, stefanha@...hat.com, amit@...nel.org,
arei.gonglei@...wei.com, airlied@...ux.ie, kraxel@...hat.com,
dan.j.williams@...el.com, johannes@...solutions.net,
ohad@...ery.com, bjorn.andersson@...aro.org, david@...hat.com,
vgoyal@...hat.com, miklos@...redi.hu, sgarzare@...hat.com,
virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 17/17] virtio_ring: Add validation for used length
On Mon, May 17, 2021 at 05:08:36PM +0800, Xie Yongji wrote:
> This adds validation for used length (might come
> from an untrusted device) when it will be used by
> virtio device driver.
>
> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> ---
> drivers/virtio/virtio_ring.c | 22 +++++++++++++++++++---
> 1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index d999a1d6d271..7d4845d06f21 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -68,11 +68,13 @@
> struct vring_desc_state_split {
> void *data; /* Data for callback. */
> struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> + u32 in_len; /* Total length of writable buffer */
> };
>
> struct vring_desc_state_packed {
> void *data; /* Data for callback. */
> struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
> + u32 in_len; /* Total length of writable buffer */
> u16 num; /* Descriptor list length. */
> u16 last; /* The last desc state in a list. */
> };
Hmm for packed it's aligned to 64 bit anyway, so we are not making it
any worse. But for split this pushes struct size up by 1/3 increasing
cache pressure.
> @@ -486,7 +488,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> struct vring_virtqueue *vq = to_vvq(_vq);
> struct scatterlist *sg;
> struct vring_desc *desc;
> - unsigned int i, n, avail, descs_used, prev, err_idx;
> + unsigned int i, n, avail, descs_used, prev, err_idx, in_len = 0;
> int head;
> bool indirect;
>
> @@ -570,6 +572,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> VRING_DESC_F_NEXT |
> VRING_DESC_F_WRITE,
> indirect);
> + in_len += sg->length;
> }
> }
> /* Last one doesn't continue. */
> @@ -604,6 +607,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>
> /* Store token and indirect buffer state. */
> vq->split.desc_state[head].data = data;
> + vq->split.desc_state[head].in_len = in_len;
> if (indirect)
> vq->split.desc_state[head].indir_desc = desc;
> else
> @@ -784,6 +788,10 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
> BAD_RING(vq, "id %u is not a head!\n", i);
> return NULL;
> }
> + if (unlikely(len && vq->split.desc_state[i].in_len < *len)) {
> + BAD_RING(vq, "id %u has invalid length: %u!\n", i, *len);
> + return NULL;
> + }
>
> /* detach_buf_split clears data, so grab it now. */
> ret = vq->split.desc_state[i].data;
> @@ -1059,7 +1067,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> {
> struct vring_packed_desc *desc;
> struct scatterlist *sg;
> - unsigned int i, n, err_idx;
> + unsigned int i, n, err_idx, in_len = 0;
> u16 head, id;
> dma_addr_t addr;
>
> @@ -1084,6 +1092,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> if (vring_mapping_error(vq, addr))
> goto unmap_release;
>
> + in_len += (n < out_sgs) ? 0 : sg->length;
> desc[i].flags = cpu_to_le16(n < out_sgs ?
> 0 : VRING_DESC_F_WRITE);
> desc[i].addr = cpu_to_le64(addr);
> @@ -1141,6 +1150,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> vq->packed.desc_state[id].data = data;
> vq->packed.desc_state[id].indir_desc = desc;
> vq->packed.desc_state[id].last = id;
> + vq->packed.desc_state[id].in_len = in_len;
>
> vq->num_added += 1;
>
> @@ -1173,7 +1183,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> struct vring_virtqueue *vq = to_vvq(_vq);
> struct vring_packed_desc *desc;
> struct scatterlist *sg;
> - unsigned int i, n, c, descs_used, err_idx;
> + unsigned int i, n, c, descs_used, err_idx, in_len = 0;
> __le16 head_flags, flags;
> u16 head, id, prev, curr, avail_used_flags;
>
> @@ -1223,6 +1233,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> if (vring_mapping_error(vq, addr))
> goto unmap_release;
>
> + in_len += (n < out_sgs) ? 0 : sg->length;
> flags = cpu_to_le16(vq->packed.avail_used_flags |
> (++c == total_sg ? 0 : VRING_DESC_F_NEXT) |
> (n < out_sgs ? 0 : VRING_DESC_F_WRITE));
> @@ -1268,6 +1279,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> vq->packed.desc_state[id].data = data;
> vq->packed.desc_state[id].indir_desc = ctx;
> vq->packed.desc_state[id].last = prev;
> + vq->packed.desc_state[id].in_len = in_len;
>
> /*
> * A driver MUST NOT make the first descriptor in the list
> @@ -1456,6 +1468,10 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
> BAD_RING(vq, "id %u is not a head!\n", id);
> return NULL;
> }
> + if (unlikely(len && vq->packed.desc_state[id].in_len < *len)) {
> + BAD_RING(vq, "id %u has invalid length: %u!\n", id, *len);
> + return NULL;
> + }
>
> /* detach_buf_packed clears data, so grab it now. */
> ret = vq->packed.desc_state[id].data;
> --
> 2.11.0
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