From 6b78351398ced3e1527405c350b5d9459b8f44f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <mdaenzer@redhat.com>
Date: Fri, 23 Jul 2021 09:58:57 +0200
Subject: dma-buf/poll: Get a file reference for outstanding fence callbacks
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Git-commit: ff2d23843f7fb4f13055be5a4a9a20ddd04e6e9c
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
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: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723075857.4065-1-michel@daenzer.net
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/dma-buf/dma-buf.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index b03588459862..44182bd911bb 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -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);
--
2.38.1