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Date: Sat, 7 Oct 2023 00:11:08 +0200
From: Michael Grzeschik <mgr@...gutronix.de>
To: Avichal Rakesh <arakesh@...gle.com>
Cc: dan.scally@...asonboard.com, gregkh@...uxfoundation.org,
laurent.pinchart@...asonboard.com, etalvala@...gle.com,
jchowdhary@...gle.com, linux-kernel@...r.kernel.org,
linux-usb@...r.kernel.org
Subject: Re: [PATCH v3 2/3] usb: gadget: uvc: Allocate uvc_requests one at a
time
On Thu, Oct 05, 2023 at 11:08:13AM -0700, 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@google.com
>Suggested-by: Michael Grzeschik <mgr@...gutronix.de>
Please use my full address here. m.grzeschik@...gutronix.de
>Signed-off-by: Avichal Rakesh <arakesh@...gle.com>
>---
>v1 -> v2: Rebased to ToT
>V2 -> V3: Fix email threading goof-up
>
> drivers/usb/gadget/function/uvc.h | 3 +-
> drivers/usb/gadget/function/uvc_video.c | 90 ++++++++++++++-----------
> 2 files changed, 51 insertions(+), 42 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 97d875c27dcf..3c4d286d81c0 100644
>--- a/drivers/usb/gadget/function/uvc_video.c
>+++ b/drivers/usb/gadget/function/uvc_video.c
>@@ -227,6 +227,23 @@ 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;
>@@ -299,27 +316,13 @@ 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);
>-
>- if (video->ureq[i].req) {
>- usb_ep_free_request(video->ep, video->ureq[i].req);
>- video->ureq[i].req = NULL;
>- }
>+ struct uvc_request *ureq, *temp;
>
>- 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);
> }
Please drop the extra braces.
>
>+ INIT_LIST_HEAD(&video->ureqs);
> INIT_LIST_HEAD(&video->req_free);
> video->req_size = 0;
> return 0;
>@@ -328,6 +331,7 @@ 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;
>@@ -338,29 +342,31 @@ uvc_video_alloc_requests(struct uvc_video *video)
> * 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) {
>- video->ureq[i].req_buffer = kmalloc(req_size, GFP_KERNEL);
>- if (video->ureq[i].req_buffer == NULL)
>+ INIT_LIST_HEAD(&video->ureqs);
>+ 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);
>+ }
>
>- video->ureq[i].req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>- if (video->ureq[i].req == NULL)
>+ list_for_each_entry(ureq, &video->ureqs, list) {
>+ ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
>+ if (ureq->req_buffer == NULL)
> goto error;
>-
Instead of looping twice. Wouldn't it be possible to fill the
just created ureq from the for loop here directly.
>- 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;
>-
>- list_add_tail(&video->ureq[i].req->list, &video->req_free);
>+ ureq->req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>+ if (ureq->req == NULL)
>+ goto error;
>+ 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;
Add an extra spare line just like in the code before.
>+ 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);
> }
>@@ -504,7 +510,7 @@ static void uvcg_video_pump(struct work_struct *work)
> int uvcg_video_enable(struct uvc_video *video, int enable)
> {
> struct uvc_device *uvc = video->uvc;
>- unsigned int i;
>+ struct uvc_request *ureq;
> int ret;
>
> if (video->ep == NULL) {
>@@ -519,9 +525,10 @@ 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);
>@@ -555,6 +562,7 @@ 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);
>--
>2.42.0.609.gbb76f46606-goog
>
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