| From 5095402b3cb8a504a47a17113fc1146450525ee1 Mon Sep 17 00:00:00 2001 |
| From: Yintian Tao <yttao@amd.com> |
| Date: Mon, 23 Mar 2020 19:19:37 +0800 |
| Subject: [PATCH] drm/scheduler: fix rare NULL ptr race |
| MIME-Version: 1.0 |
| Content-Type: text/plain; charset=UTF-8 |
| Content-Transfer-Encoding: 8bit |
| |
| commit 77bb2f204f1f0a53a602a8fd15816d6826212077 upstream. |
| |
| There is one one corner case at dma_fence_signal_locked |
| which will raise the NULL pointer problem just like below. |
| ->dma_fence_signal |
| ->dma_fence_signal_locked |
| ->test_and_set_bit |
| here trigger dma_fence_release happen due to the zero of fence refcount. |
| |
| ->dma_fence_put |
| ->dma_fence_release |
| ->drm_sched_fence_release_scheduled |
| ->call_rcu |
| here make the union fled “cb_list” at finished fence |
| to NULL because struct rcu_head contains two pointer |
| which is same as struct list_head cb_list |
| |
| Therefore, to hold the reference of finished fence at drm_sched_process_job |
| to prevent the null pointer during finished fence dma_fence_signal |
| |
| [ 732.912867] BUG: kernel NULL pointer dereference, address: 0000000000000008 |
| [ 732.914815] #PF: supervisor write access in kernel mode |
| [ 732.915731] #PF: error_code(0x0002) - not-present page |
| [ 732.916621] PGD 0 P4D 0 |
| [ 732.917072] Oops: 0002 [#1] SMP PTI |
| [ 732.917682] CPU: 7 PID: 0 Comm: swapper/7 Tainted: G OE 5.4.0-rc7 #1 |
| [ 732.918980] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014 |
| [ 732.920906] RIP: 0010:dma_fence_signal_locked+0x3e/0x100 |
| [ 732.938569] Call Trace: |
| [ 732.939003] <IRQ> |
| [ 732.939364] dma_fence_signal+0x29/0x50 |
| [ 732.940036] drm_sched_fence_finished+0x12/0x20 [gpu_sched] |
| [ 732.940996] drm_sched_process_job+0x34/0xa0 [gpu_sched] |
| [ 732.941910] dma_fence_signal_locked+0x85/0x100 |
| [ 732.942692] dma_fence_signal+0x29/0x50 |
| [ 732.943457] amdgpu_fence_process+0x99/0x120 [amdgpu] |
| [ 732.944393] sdma_v4_0_process_trap_irq+0x81/0xa0 [amdgpu] |
| |
| v2: hold the finished fence at drm_sched_process_job instead of |
| amdgpu_fence_process |
| v3: resume the blank line |
| |
| Signed-off-by: Yintian Tao <yttao@amd.com> |
| Reviewed-by: Christian König <christian.koenig@amd.com> |
| Signed-off-by: Alex Deucher <alexander.deucher@amd.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c |
| index a3688a5c166a..eba7731ce681 100644 |
| --- a/drivers/gpu/drm/scheduler/sched_main.c |
| +++ b/drivers/gpu/drm/scheduler/sched_main.c |
| @@ -618,7 +618,9 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb) |
| list_del_init(&s_job->node); |
| spin_unlock_irqrestore(&sched->job_list_lock, flags); |
| |
| + dma_fence_get(&s_fence->finished); |
| drm_sched_fence_finished(s_fence); |
| + dma_fence_put(&s_fence->finished); |
| |
| trace_drm_sched_process_job(s_fence); |
| wake_up_interruptible(&sched->wake_up_worker); |
| -- |
| 2.7.4 |
| |
