Re: [PATCH v9 2/4] usb: gadget: uvc: Allocate uvc_requests one at a time
From: Avichal Rakesh
Date: Mon Oct 30 2023 - 16:26:47 EST
On 10/28/23 13:13, Dan Scally wrote:
> Hi Avichal
>
> On 27/10/2023 21:19, Avichal Rakesh wrote:
>> Currently, the uvc gadget driver allocates all uvc_requests as one array
>> and deallocates them all when the video stream stops. This includes
>> de-allocating all the usb_requests associated with those uvc_requests.
>> This can lead to use-after-free issues if any of those de-allocated
>> usb_requests were still owned by the usb controller.
>>
>> This patch is 1 of 2 patches addressing the use-after-free issue.
>> Instead of bulk allocating all uvc_requests as an array, this patch
>> allocates uvc_requests one at a time, which should allows for similar
>> granularity when deallocating the uvc_requests. This patch has no
>> functional changes other than allocating each uvc_request separately,
>> and similarly freeing each of them separately.
>>
>> Link: https://lore.kernel.org/7cd81649-2795-45b6-8c10-b7df1055020d@xxxxxxxxxx
>> Suggested-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
>> Reviewed-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
>
>
> Sorry - I was unclear in my response to the first patch on v8. I meant my R-b to apply to the first patch only rather than to all of them. For this one I understand now the use of the conditional in uvc_video_free_request(), so that point is fine. I agree with Greg that the BUG_ON() shouldn't stand though.
Ah, didn't realize BUG_ON is discouraged. Removed BUG_ON.
It was supposed to be a defensive bit of code anyway,
so removing the check entirely. If the state is
inconsistent, we'd see other errors, so the BUG_ON
wasn't providing value anyway.
Also removed your Reviewed-by, my apologies.
>
>> Reviewed-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
>> Tested-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
>> Signed-off-by: Avichal Rakesh <arakesh@xxxxxxxxxx>
>> ---
>> v1 -> v2: Rebased to ToT
>> v2 -> v3: Fix email threading goof-up
>> v3 -> v4: Address review comments & re-rebase to ToT
>> v4 -> v5: Address more review comments. Add Reviewed-by & Tested-by.
>> v5 -> v6: No change
>> v6 -> v7: No change
>> v7 -> v8: No change. Getting back in review queue
>> v8 -> v9: Address review comments.
>>
>> drivers/usb/gadget/function/uvc.h | 3 +-
>> drivers/usb/gadget/function/uvc_video.c | 89 ++++++++++++++-----------
>> 2 files changed, 52 insertions(+), 40 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
>> index 989bc6b4e93d..993694da0bbc 100644
>> --- a/drivers/usb/gadget/function/uvc.h
>> +++ b/drivers/usb/gadget/function/uvc.h
>> @@ -81,6 +81,7 @@ struct uvc_request {
>> struct sg_table sgt;
>> u8 header[UVCG_REQUEST_HEADER_LEN];
>> struct uvc_buffer *last_buf;
>> + struct list_head list;
>> };
>>
>> struct uvc_video {
>> @@ -102,7 +103,7 @@ struct uvc_video {
>>
>> /* Requests */
>> unsigned int req_size;
>> - struct uvc_request *ureq;
>> + struct list_head ureqs; /* all uvc_requests allocated by uvc_video */
>> struct list_head req_free;
>> spinlock_t req_lock;
>>
>> diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
>> index c334802ac0a4..f8f9209fee50 100644
>> --- a/drivers/usb/gadget/function/uvc_video.c
>> +++ b/drivers/usb/gadget/function/uvc_video.c
>> @@ -227,6 +227,24 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
>> * Request handling
>> */
>>
>> +static void
>> +uvc_video_free_request(struct uvc_request *ureq, struct usb_ep *ep)
>> +{
>> + sg_free_table(&ureq->sgt);
>> + if (ureq->req && ep) {
>> + usb_ep_free_request(ep, ureq->req);
>> + ureq->req = NULL;
>> + }
>> +
>> + kfree(ureq->req_buffer);
>> + ureq->req_buffer = NULL;
>> +
>> + if (!list_empty(&ureq->list))
>> + list_del_init(&ureq->list);
>> +
>> + kfree(ureq);
>> +}
>> +
>> static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
>> {
>> int ret;
>> @@ -293,27 +311,12 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
>> static int
>> uvc_video_free_requests(struct uvc_video *video)
>> {
>> - unsigned int i;
>> -
>> - if (video->ureq) {
>> - for (i = 0; i < video->uvc_num_requests; ++i) {
>> - sg_free_table(&video->ureq[i].sgt);
>> + struct uvc_request *ureq, *temp;
>>
>> - if (video->ureq[i].req) {
>> - usb_ep_free_request(video->ep, video->ureq[i].req);
>> - video->ureq[i].req = NULL;
>> - }
>> -
>> - if (video->ureq[i].req_buffer) {
>> - kfree(video->ureq[i].req_buffer);
>> - video->ureq[i].req_buffer = NULL;
>> - }
>> - }
>> -
>> - kfree(video->ureq);
>> - video->ureq = NULL;
>> - }
>> + list_for_each_entry_safe(ureq, temp, &video->ureqs, list)
>> + uvc_video_free_request(ureq, video->ep);
>>
>> + INIT_LIST_HEAD(&video->ureqs);
>> INIT_LIST_HEAD(&video->req_free);
>> video->req_size = 0;
>> return 0;
>> @@ -322,39 +325,45 @@ uvc_video_free_requests(struct uvc_video *video)
>> static int
>> uvc_video_alloc_requests(struct uvc_video *video)
>> {
>> + struct uvc_request *ureq;
>> unsigned int req_size;
>> unsigned int i;
>> int ret = -ENOMEM;
>>
>> BUG_ON(video->req_size);
>> + BUG_ON(!list_empty(&video->ureqs));
>>
>> req_size = video->ep->maxpacket
>> * max_t(unsigned int, video->ep->maxburst, 1)
>> * (video->ep->mult);
>>
>> - video->ureq = kcalloc(video->uvc_num_requests, sizeof(struct uvc_request), GFP_KERNEL);
>> - if (video->ureq == NULL)
>> - return -ENOMEM;
>> + for (i = 0; i < video->uvc_num_requests; i++) {
>> + ureq = kzalloc(sizeof(struct uvc_request), GFP_KERNEL);
>> + if (ureq == NULL)
>> + goto error;
>> +
>> + INIT_LIST_HEAD(&ureq->list);
>> +
>> + list_add_tail(&ureq->list, &video->ureqs);
>>
>> - for (i = 0; i < video->uvc_num_requests; ++i) {
>> - video->ureq[i].req_buffer = kmalloc(req_size, GFP_KERNEL);
>> - if (video->ureq[i].req_buffer == NULL)
>> + ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
>> + if (ureq->req_buffer == NULL)
>> goto error;
>>
>> - video->ureq[i].req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>> - if (video->ureq[i].req == NULL)
>> + ureq->req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>> + if (ureq->req == NULL)
>> goto error;
>>
>> - video->ureq[i].req->buf = video->ureq[i].req_buffer;
>> - video->ureq[i].req->length = 0;
>> - video->ureq[i].req->complete = uvc_video_complete;
>> - video->ureq[i].req->context = &video->ureq[i];
>> - video->ureq[i].video = video;
>> - video->ureq[i].last_buf = NULL;
>> + ureq->req->buf = ureq->req_buffer;
>> + ureq->req->length = 0;
>> + ureq->req->complete = uvc_video_complete;
>> + ureq->req->context = ureq;
>> + ureq->video = video;
>> + ureq->last_buf = NULL;
>>
>> - list_add_tail(&video->ureq[i].req->list, &video->req_free);
>> + list_add_tail(&ureq->req->list, &video->req_free);
>> /* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
>> - sg_alloc_table(&video->ureq[i].sgt,
>> + sg_alloc_table(&ureq->sgt,
>> DIV_ROUND_UP(req_size - UVCG_REQUEST_HEADER_LEN,
>> PAGE_SIZE) + 2, GFP_KERNEL);
>> }
>> @@ -489,8 +498,8 @@ static void uvcg_video_pump(struct work_struct *work)
>> */
>> int uvcg_video_enable(struct uvc_video *video, int enable)
>> {
>> - unsigned int i;
>> int ret;
>> + struct uvc_request *ureq;
>>
>> if (video->ep == NULL) {
>> uvcg_info(&video->uvc->func,
>> @@ -502,9 +511,10 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
>> cancel_work_sync(&video->pump);
>> uvcg_queue_cancel(&video->queue, 0);
>>
>> - for (i = 0; i < video->uvc_num_requests; ++i)
>> - if (video->ureq && video->ureq[i].req)
>> - usb_ep_dequeue(video->ep, video->ureq[i].req);
>> + list_for_each_entry(ureq, &video->ureqs, list) {
>> + if (ureq->req)
>> + usb_ep_dequeue(video->ep, ureq->req);
>> + }
>>
>> uvc_video_free_requests(video);
>> uvcg_queue_enable(&video->queue, 0);
>> @@ -536,6 +546,7 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
>> */
>> int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
>> {
>> + INIT_LIST_HEAD(&video->ureqs);
>> INIT_LIST_HEAD(&video->req_free);
>> spin_lock_init(&video->req_lock);
>> INIT_WORK(&video->pump, uvcg_video_pump);
>> --
>> 2.42.0.820.g83a721a137-goog