5.15-stable review patch. If anyone has any objections, please let me know.
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From: Abhinav Singh singhabhinav9051571833@gmail.com
[ Upstream commit 5f35a624c1e30b5bae5023b3c256e94e0ad4f806 ]
Fix a sparse warning with this message "warning:dereference of noderef expression". In this context it means we are dereferencing a __rcu tagged pointer directly.
We should not be directly dereferencing a rcu pointer. To get a normal (non __rcu tagged pointer) from a __rcu tagged pointer we are using the function unrcu_pointer(...). The non __rcu tagged pointer then can be dereferenced just like a normal pointer.
I tested with qemu with this command qemu-system-x86_64 \ -m 2G \ -smp 2 \ -kernel bzImage \ -append "console=ttyS0 root=/dev/sda earlyprintk=serial net.ifnames=0" \ -drive file=bullseye.img,format=raw \ -net user,host=10.0.2.10,hostfwd=tcp:127.0.0.1:10021-:22 \ -net nic,model=e1000 \ -enable-kvm \ -nographic \ -pidfile vm.pid \ 2>&1 | tee vm.log with lockdep enabled.
Fixes: 0ec5f02f0e2c ("drm/nouveau: prevent stale fence->channel pointers, and protect with rcu") Signed-off-by: Abhinav Singh singhabhinav9051571833@gmail.com Signed-off-by: Danilo Krummrich dakr@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/20231113191303.3277733-1-singh... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/nouveau/nv04_fence.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nv04_fence.c b/drivers/gpu/drm/nouveau/nv04_fence.c index 5b71a5a5cd85..cdbc75e3d1f6 100644 --- a/drivers/gpu/drm/nouveau/nv04_fence.c +++ b/drivers/gpu/drm/nouveau/nv04_fence.c @@ -39,7 +39,7 @@ struct nv04_fence_priv { static int nv04_fence_emit(struct nouveau_fence *fence) { - struct nvif_push *push = fence->channel->chan.push; + struct nvif_push *push = unrcu_pointer(fence->channel)->chan.push; int ret = PUSH_WAIT(push, 2); if (ret == 0) { PUSH_NVSQ(push, NV_SW, 0x0150, fence->base.seqno);