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dma-buf: insert memory barrier before updating num_fences

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smp_store_mb() inserts memory barrier after storing operation.
It is different with what the comment is originally aiming so Null
pointer dereference can be happened if memory update is reordered.

Signed-off-by: Hyejeong Choi <hjeong.choi@samsung.com>
Fixes: a590d0fdbaa5 ("dma-buf: Update reservation shared_count after adding the new fence")
CC: stable@vger.kernel.org
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20250513020638.GA2329653@au1-maretx-p37.eng.sarc.samsung.com
Signed-off-by: Christian König <christian.koenig@amd.com>
This commit is contained in:
Hyejeong Choi 2025-05-12 21:06:38 -05:00 committed by Christian König
parent 2f0c6fceae
commit 72c7d62583
1 changed files with 3 additions and 2 deletions
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5
drivers/dma-buf/dma-resv.c
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@ -320,8 +320,9 @@ void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
count++;
dma_resv_list_set(fobj, i, fence, usage);
/* pointer update must be visible before we extend the num_fences */
smp_store_mb(fobj->num_fences, count);
/* fence update must be visible before we extend the num_fences */
smp_wmb();
fobj->num_fences = count;
}
EXPORT_SYMBOL(dma_resv_add_fence);