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| author | Gustavo Padovan <gustavo.padovan@collabora.com> | 2017-07-29 18:22:16 +0300 |
|---|---|---|
| committer | Gustavo Padovan <gustavo.padovan@collabora.com> | 2017-07-31 20:11:15 +0300 |
| commit | 3792b7c1a70815fe4e954221c096f9278638fd21 (patch) | |
| tree | 4bbd50bc1eaa3e450f3258d78f64dccc735064a4 /drivers/dma-buf | |
| parent | 150b6a9d7d6fffb95c0a5349960a10569e8218b5 (diff) | |
| download | linux-3792b7c1a70815fe4e954221c096f9278638fd21.tar.xz | |
dma-buf/sw_sync: clean up list before signaling the fence
If userspace already dropped its own reference by closing the sw_sync
fence fd we might end up in a deadlock where
dma_fence_is_signaled_locked() will trigger the release of the fence and
thus try to hold the lock to remove the fence from the list.
dma_fence_is_signaled_locked() tries to release/free the fence and hold
the lock in the process.
We fix that by changing the order operation and clean up the list and
rb-tree first.
v2: Drop fence get/put dance and manipulate the list first (Chris Wilson)
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170729152217.8362-2-gustavo@padovan.org
Diffstat (limited to 'drivers/dma-buf')
| -rw-r--r-- | drivers/dma-buf/sw_sync.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index ef0cc08f5dfb..38cc7389a6c1 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -213,11 +213,21 @@ static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc) obj->value += inc; list_for_each_entry_safe(pt, next, &obj->pt_list, link) { - if (!dma_fence_is_signaled_locked(&pt->base)) + if (!timeline_fence_signaled(&pt->base)) break; list_del_init(&pt->link); rb_erase(&pt->node, &obj->pt_tree); + + /* + * A signal callback may release the last reference to this + * fence, causing it to be freed. That operation has to be + * last to avoid a use after free inside this loop, and must + * be after we remove the fence from the timeline in order to + * prevent deadlocking on timeline->lock inside + * timeline_fence_release(). + */ + dma_fence_signal_locked(&pt->base); } spin_unlock_irq(&obj->lock); |