Am 04.06.19 um 14:39 schrieb Chris Wilson:

If we have to drop the seqcount & rcu lock to perform a krealloc, we have to restart the loop. In doing so, be careful not to lose track of the already acquired exclusive fence.

Fixes: fedf54132d24 ("dma-buf: Restart reservation_object_get_fences_rcu() after writes") #v4.10 Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Cc: Christian König christian.koenig@amd.com Cc: Alex Deucher alexander.deucher@amd.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: stable@vger.kernel.org

---

drivers/dma-buf/reservation.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 4d32e2c67862..704503df4892 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -365,6 +365,12 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, GFP_NOWAIT | __GFP_NOWARN); if (!nshared) { rcu_read_unlock();

• 		if (fence_excl) {
  

• 			dma_fence_put(fence_excl);
  

• 			fence_excl = NULL;
  

• 		}
  

dma_fence_put is NULL save, so no need for the if.

But apart from that a good catch, Christian.

		nshared = krealloc(shared, sz, GFP_KERNEL);
		if (nshared) {
			shared = nshared;

If we have to drop the seqcount & rcu lock to perform a krealloc, we have to restart the loop. In doing so, be careful not to lose track of the already acquired exclusive fence.

Fixes: fedf54132d24 ("dma-buf: Restart reservation_object_get_fences_rcu() after writes") #v4.10 Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Cc: Christian König christian.koenig@amd.com Cc: Alex Deucher alexander.deucher@amd.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: stable@vger.kernel.org Reviewed-by: Christian König christian.koenig@amd.com --- This, this is v2. Not the old branch; remember to check the git send-email before hitting enter. -Chris --- drivers/dma-buf/reservation.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 4d32e2c67862..4447e13d1e89 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -365,6 +365,10 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, GFP_NOWAIT | __GFP_NOWARN); if (!nshared) { rcu_read_unlock(); + + dma_fence_put(fence_excl); + fence_excl = NULL; + nshared = krealloc(shared, sz, GFP_KERNEL); if (nshared) { shared = nshared;