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From 0138bee3c72c96d6aaedce02f5691730ec81571d Mon Sep 17 00:00:00 2001
From: Dave Airlie <airlied@redhat.com>
Date: Thu, 15 Jun 2023 12:22:11 +1000
Subject: [PATCH] nouveau: fix client work fence deletion race
This seems to have existed for ever but is now more apparant after
9bff18d13473a9fdf81d5158248472a9d8ecf2bd (drm/ttm: use per BO cleanup workers)
My analysis:
two threads are running,
one in the irq signalling the fence, in dma_fence_signal_timestamp_locked,
it has done the DMA_FENCE_FLAG_SIGNALLED_BIT setting, but hasn't yet reached the callbacks.
second thread in nouveau_cli_work_ready, where it sees the fence is signalled, so then puts the
fence, cleanups the object and frees the work item, which contains the callback.
thread one goes again and tries to call the callback and causes the use-after-free.
Proposed fix:
lock the fence signalled check in nouveau_cli_work_ready, so either the callbacks are done
or the memory is freed.
Signed-off-by: Dave Airlie <airlied@redhat.com>
---
drivers/gpu/drm/nouveau/nouveau_drm.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index cc7c5b4a05fd..1a45be769848 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -137,10 +137,16 @@ nouveau_name(struct drm_device *dev)
static inline bool
nouveau_cli_work_ready(struct dma_fence *fence)
{
- if (!dma_fence_is_signaled(fence))
- return false;
- dma_fence_put(fence);
- return true;
+ unsigned long flags;
+ bool ret = true;
+ spin_lock_irqsave(fence->lock, flags);
+ if (!dma_fence_is_signaled_locked(fence))
+ ret = false;
+ spin_unlock_irqrestore(fence->lock, flags);
+
+ if (ret == true)
+ dma_fence_put(fence);
+ return ret;
}
static void
--
2.40.1
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