dma-buf: Discard old fence_excl on retrying get_fences_rcu for realloc

commit f5b07b04e5f090a85d1e96938520f2b2b58e4a8e upstream.

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")
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 #v4.10
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190604125323.21396-1-chris@chris-wilson.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index c1618335ca9944e11c537eb7bd2c13ed3dd93b2b..03004a218ec14db6b2b60e223135c1696147cd1c 100644 (file)
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -357,6 +357,10 @@ 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;