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Tsirkin" To: Jason Wang Cc: virtualization , linux-kernel , "Hetzelt, Felicitas" , "kaplan, david" , Konrad Rzeszutek Wilk Subject: Re: [PATCH V4 1/4] virtio_ring: validate used buffer length Message-ID: <20211026063231-mutt-send-email-mst@kernel.org> References: <20211026072000.8699-1-jasowang@redhat.com> <20211026072000.8699-2-jasowang@redhat.com> <20211026053741-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 26, 2021 at 06:21:46PM +0800, Jason Wang wrote: > On Tue, Oct 26, 2021 at 5:44 PM Michael S. Tsirkin wrote: > > > > On Tue, Oct 26, 2021 at 03:19:57PM +0800, Jason Wang wrote: > > > This patch validate the used buffer length provided by the device > > > before trying to use it. This is done by record the in buffer length > > > in a new field in desc_state structure during virtqueue_add(), then we > > > can fail the virtqueue_get_buf() when we find the device is trying to > > > give us a used buffer length which is greater than the in buffer > > > length. > > > > > > Since some drivers have already done the validation by themselves, > > > this patch tries to makes the core validation optional. For the driver > > > that doesn't want the validation, it can set the validate_used to be > > > true (which could be overridden by force_used_validation). To be more > > > > This description is now out of date. it's suppress_used_validation. > > Yes, do you want me to post a new version or do you want to fix it for me? > > Thanks repost pls > > > > > efficient, a dedicate array is used for storing the validate used > > > length, this helps to eliminate the cache stress if validation is done > > > by the driver. > > > > > > Signed-off-by: Jason Wang > > > --- > > > drivers/virtio/virtio_ring.c | 60 ++++++++++++++++++++++++++++++++++++ > > > include/linux/virtio.h | 2 ++ > > > 2 files changed, 62 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > index 4c0ec82cef56..a6e5a3b94337 100644 > > > --- a/drivers/virtio/virtio_ring.c > > > +++ b/drivers/virtio/virtio_ring.c > > > @@ -14,6 +14,9 @@ > > > #include > > > #include > > > > > > +static bool force_used_validation = false; > > > +module_param(force_used_validation, bool, 0444); > > > + > > > #ifdef DEBUG > > > /* For development, we want to crash whenever the ring is screwed. */ > > > #define BAD_RING(_vq, fmt, args...) \ > > > @@ -182,6 +185,9 @@ struct vring_virtqueue { > > > } packed; > > > }; > > > > > > + /* Per-descriptor in buffer length */ > > > + u32 *buflen; > > > + > > > /* How to notify other side. FIXME: commonalize hcalls! */ > > > bool (*notify)(struct virtqueue *vq); > > > > > > @@ -490,6 +496,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > > unsigned int i, n, avail, descs_used, prev, err_idx; > > > int head; > > > bool indirect; > > > + u32 buflen = 0; > > > > > > START_USE(vq); > > > > > > @@ -571,6 +578,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > > VRING_DESC_F_NEXT | > > > VRING_DESC_F_WRITE, > > > indirect); > > > + buflen += sg->length; > > > } > > > } > > > /* Last one doesn't continue. */ > > > @@ -610,6 +618,10 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > > else > > > vq->split.desc_state[head].indir_desc = ctx; > > > > > > + /* Store in buffer length if necessary */ > > > + if (vq->buflen) > > > + vq->buflen[head] = buflen; > > > + > > > /* Put entry in available array (but don't update avail->idx until they > > > * do sync). */ > > > avail = vq->split.avail_idx_shadow & (vq->split.vring.num - 1); > > > @@ -784,6 +796,11 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq, > > > BAD_RING(vq, "id %u is not a head!\n", i); > > > return NULL; > > > } > > > + if (vq->buflen && unlikely(*len > vq->buflen[i])) { > > > + BAD_RING(vq, "used len %d is larger than in buflen %u\n", > > > + *len, vq->buflen[i]); > > > + return NULL; > > > + } > > > > > > /* detach_buf_split clears data, so grab it now. */ > > > ret = vq->split.desc_state[i].data; > > > @@ -1062,6 +1079,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > > unsigned int i, n, err_idx; > > > u16 head, id; > > > dma_addr_t addr; > > > + u32 buflen = 0; > > > > > > head = vq->packed.next_avail_idx; > > > desc = alloc_indirect_packed(total_sg, gfp); > > > @@ -1091,6 +1109,8 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > > desc[i].addr = cpu_to_le64(addr); > > > desc[i].len = cpu_to_le32(sg->length); > > > i++; > > > + if (n >= out_sgs) > > > + buflen += sg->length; > > > } > > > } > > > > > > @@ -1144,6 +1164,10 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > > vq->packed.desc_state[id].indir_desc = desc; > > > vq->packed.desc_state[id].last = id; > > > > > > + /* Store in buffer length if necessary */ > > > + if (vq->buflen) > > > + vq->buflen[id] = buflen; > > > + > > > vq->num_added += 1; > > > > > > pr_debug("Added buffer head %i to %p\n", head, vq); > > > @@ -1179,6 +1203,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > > __le16 head_flags, flags; > > > u16 head, id, prev, curr, avail_used_flags; > > > int err; > > > + u32 buflen = 0; > > > > > > START_USE(vq); > > > > > > @@ -1258,6 +1283,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > > 1 << VRING_PACKED_DESC_F_AVAIL | > > > 1 << VRING_PACKED_DESC_F_USED; > > > } > > > + if (n >= out_sgs) > > > + buflen += sg->length; > > > } > > > } > > > > > > @@ -1277,6 +1304,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > > vq->packed.desc_state[id].indir_desc = ctx; > > > vq->packed.desc_state[id].last = prev; > > > > > > + /* Store in buffer length if necessary */ > > > + if (vq->buflen) > > > + vq->buflen[id] = buflen; > > > + > > > /* > > > * A driver MUST NOT make the first descriptor in the list > > > * available before all subsequent descriptors comprising > > > @@ -1463,6 +1494,11 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > > > BAD_RING(vq, "id %u is not a head!\n", id); > > > return NULL; > > > } > > > + if (vq->buflen && unlikely(*len > vq->buflen[id])) { > > > + BAD_RING(vq, "used len %d is larger than in buflen %u\n", > > > + *len, vq->buflen[id]); > > > + return NULL; > > > + } > > > > > > /* detach_buf_packed clears data, so grab it now. */ > > > ret = vq->packed.desc_state[id].data; > > > @@ -1668,6 +1704,7 @@ static struct virtqueue *vring_create_virtqueue_packed( > > > struct vring_virtqueue *vq; > > > struct vring_packed_desc *ring; > > > struct vring_packed_desc_event *driver, *device; > > > + struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver); > > > dma_addr_t ring_dma_addr, driver_event_dma_addr, device_event_dma_addr; > > > size_t ring_size_in_bytes, event_size_in_bytes; > > > > > > @@ -1757,6 +1794,15 @@ static struct virtqueue *vring_create_virtqueue_packed( > > > if (!vq->packed.desc_extra) > > > goto err_desc_extra; > > > > > > + if (!drv->suppress_used_validation || force_used_validation) { > > > + vq->buflen = kmalloc_array(num, sizeof(*vq->buflen), > > > + GFP_KERNEL); > > > + if (!vq->buflen) > > > + goto err_buflen; > > > + } else { > > > + vq->buflen = NULL; > > > + } > > > + > > > /* No callback? Tell other side not to bother us. */ > > > if (!callback) { > > > vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE; > > > @@ -1769,6 +1815,8 @@ static struct virtqueue *vring_create_virtqueue_packed( > > > spin_unlock(&vdev->vqs_list_lock); > > > return &vq->vq; > > > > > > +err_buflen: > > > + kfree(vq->packed.desc_extra); > > > err_desc_extra: > > > kfree(vq->packed.desc_state); > > > err_desc_state: > > > @@ -2176,6 +2224,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > void (*callback)(struct virtqueue *), > > > const char *name) > > > { > > > + struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver); > > > struct vring_virtqueue *vq; > > > > > > if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)) > > > @@ -2235,6 +2284,15 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > if (!vq->split.desc_extra) > > > goto err_extra; > > > > > > + if (!drv->suppress_used_validation || force_used_validation) { > > > + vq->buflen = kmalloc_array(vring.num, sizeof(*vq->buflen), > > > + GFP_KERNEL); > > > + if (!vq->buflen) > > > + goto err_buflen; > > > + } else { > > > + vq->buflen = NULL; > > > + } > > > + > > > /* Put everything in free lists. */ > > > vq->free_head = 0; > > > memset(vq->split.desc_state, 0, vring.num * > > > @@ -2245,6 +2303,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > spin_unlock(&vdev->vqs_list_lock); > > > return &vq->vq; > > > > > > +err_buflen: > > > + kfree(vq->split.desc_extra); > > > err_extra: > > > kfree(vq->split.desc_state); > > > err_state: > > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > > index 41edbc01ffa4..44d0e09da2d9 100644 > > > --- a/include/linux/virtio.h > > > +++ b/include/linux/virtio.h > > > @@ -152,6 +152,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev); > > > * @feature_table_size: number of entries in the feature table array. > > > * @feature_table_legacy: same as feature_table but when working in legacy mode. > > > * @feature_table_size_legacy: number of entries in feature table legacy array. > > > + * @suppress_used_validation: set to not have core validate used length > > > * @probe: the function to call when a device is found. Returns 0 or -errno. > > > * @scan: optional function to call after successful probe; intended > > > * for virtio-scsi to invoke a scan. > > > @@ -168,6 +169,7 @@ struct virtio_driver { > > > unsigned int feature_table_size; > > > const unsigned int *feature_table_legacy; > > > unsigned int feature_table_size_legacy; > > > + bool suppress_used_validation; > > > int (*validate)(struct virtio_device *dev); > > > int (*probe)(struct virtio_device *dev); > > > void (*scan)(struct virtio_device *dev); > > > -- > > > 2.25.1 > >