From acc91ef94bb97f631f7e412d4436d99351ac3bfa Mon Sep 17 00:00:00 2001 From: Hyejeong Choi Date: Mon, 12 May 2025 05:16:37 -0500 Subject: [PATCH] FROMGIT: dma-buf: insert memory barrier before updating num_fences 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 Bug: 417615398 (cherry picked from commit 72c7d62583ebce7baeb61acce6057c361f73be4a https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-fixes) Change-Id: I7a984743f929fb8120d0efcf991087e4f8d489ae Signed-off-by: Hyejeong Choi --- drivers/dma-buf/dma-resv.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 5f8d010516f0..b1ef4546346d 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -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);