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Date: Tue, 25 May 2021 09:31:33 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
Xie Yongji <xieyongji@...edance.com>
Cc: 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
在 2021/5/18 上午7:39, Michael S. Tsirkin 写道:
> 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.
We can eliminate this by validating through virtio device driver instead
of virtio core.
E.g for virtio-net we know the rx buffer size so there's no need to
store in twice in the core.
Thanks
>
>
>> @@ -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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