Commit ff2d2384 authored by Michel Dänzer's avatar Michel Dänzer Committed by Christian König
Browse files

dma-buf/poll: Get a file reference for outstanding fence callbacks 



This makes sure we don't hit the

	BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);

in dma_buf_release, which could be triggered by user space closing the
dma-buf file description while there are outstanding fence callbacks
from dma_buf_poll.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarMichel Dänzer <mdaenzer@redhat.com>
Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723075857.4065-1-michel@daenzer.net


Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
parent b3ec8cdf

drivers/dma-buf/dma-buf.c

+12 −6
Original line number Diff line number Diff line
@@ -67,12 +67,9 @@ static void dma_buf_release(struct dentry *dentry) 
	BUG_ON(dmabuf->vmapping_counter);



	/*

	 * Any fences that a dma-buf poll can wait on should be signaled

	 * before releasing dma-buf. This is the responsibility of each

	 * driver that uses the reservation objects.

	 *

	 * If you hit this BUG() it means someone dropped their ref to the

	 * dma-buf while still having pending operation to the buffer.

	 * If you hit this BUG() it could mean:

	 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else

	 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback

	 */

	BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
@@ -200,6 +197,7 @@ static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) 
static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)

{

	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;

	struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);

	unsigned long flags;



	spin_lock_irqsave(&dcb->poll->lock, flags);
@@ -207,6 +205,8 @@ static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) 
	dcb->active = 0;

	spin_unlock_irqrestore(&dcb->poll->lock, flags);

	dma_fence_put(fence);

	/* Paired with get_file in dma_buf_poll */

	fput(dmabuf->file);

}



static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write,
@@ -259,6 +259,9 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) 
		spin_unlock_irq(&dmabuf->poll.lock);



		if (events & EPOLLOUT) {

			/* Paired with fput in dma_buf_poll_cb */

			get_file(dmabuf->file);



			if (!dma_buf_poll_add_cb(resv, true, dcb))

				/* No callback queued, wake up any other waiters */

				dma_buf_poll_cb(NULL, &dcb->cb);
@@ -279,6 +282,9 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) 
		spin_unlock_irq(&dmabuf->poll.lock);



		if (events & EPOLLIN) {

			/* Paired with fput in dma_buf_poll_cb */

			get_file(dmabuf->file);



			if (!dma_buf_poll_add_cb(resv, false, dcb))

				/* No callback queued, wake up any other waiters */

				dma_buf_poll_cb(NULL, &dcb->cb);