[PATCH 2/3] drm/amdgpu: fix the fence timeline null pointer

[Christian König]

Am 13.12.21 um 07:34 schrieb Huang Rui:
> Initialize the flags for embedded fence in the job at dma_fence_init().
> Otherwise, we will go a wrong way in amdgpu_fence_get_timeline_name
> callback and trigger a null pointer panic once we enabled the trace event
> here.
>
> [  156.131790] BUG: kernel NULL pointer dereference, address: 00000000000002a0
> [  156.131804] #PF: supervisor read access in kernel mode
> [  156.131811] #PF: error_code(0x0000) - not-present page
> [  156.131817] PGD 0 P4D 0
> [  156.131824] Oops: 0000 [#1] PREEMPT SMP PTI
> [  156.131832] CPU: 6 PID: 1404 Comm: sdma0 Tainted: G           OE     5.16.0-rc1-custom #1
> [  156.131842] Hardware name: Gigabyte Technology Co., Ltd. Z170XP-SLI/Z170XP-SLI-CF, BIOS F20 11/04/2016
> [  156.131848] RIP: 0010:strlen+0x0/0x20
> [  156.131859] Code: 89 c0 c3 0f 1f 80 00 00 00 00 48 01 fe eb 0f 0f b6 07 38 d0 74 10 48 83 c7 01 84 c0 74 05 48 39 f7 75 ec 31 c0 c3 48 89 f8 c3 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 c3 31
> [  156.131872] RSP: 0018:ffff9bd0018dbcf8 EFLAGS: 00010206
> [  156.131880] RAX: 00000000000002a0 RBX: ffff8d0305ef01b0 RCX: 000000000000000b
> [  156.131888] RDX: ffff8d03772ab924 RSI: ffff8d0305ef01b0 RDI: 00000000000002a0
> [  156.131895] RBP: ffff9bd0018dbd60 R08: ffff8d03002094d0 R09: 0000000000000000
> [  156.131901] R10: 000000000000005e R11: 0000000000000065 R12: ffff8d03002094d0
> [  156.131907] R13: 000000000000001f R14: 0000000000070018 R15: 0000000000000007
> [  156.131914] FS:  0000000000000000(0000) GS:ffff8d062ed80000(0000) knlGS:0000000000000000
> [  156.131923] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  156.131929] CR2: 00000000000002a0 CR3: 000000001120a005 CR4: 00000000003706e0
> [  156.131937] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  156.131942] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  156.131949] Call Trace:
> [  156.131953]  <TASK>
> [  156.131957]  ? trace_event_raw_event_dma_fence+0xcc/0x200
> [  156.131973]  ? ring_buffer_unlock_commit+0x23/0x130
> [  156.131982]  dma_fence_init+0x92/0xb0
> [  156.131993]  amdgpu_fence_emit+0x10d/0x2b0 [amdgpu]
> [  156.132302]  amdgpu_ib_schedule+0x2f9/0x580 [amdgpu]
> [  156.132586]  amdgpu_job_run+0xed/0x220 [amdgpu]
>
> Signed-off-by: Huang Rui <ray.huang at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 17 +++++++++--------
>   1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index 3b7e86ea7167..e2aa71904278 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -76,7 +76,7 @@ void amdgpu_fence_slab_fini(void)
>   /*
>    * Cast helper
>    */
> -static const struct dma_fence_ops amdgpu_fence_ops;
> +static struct dma_fence_ops amdgpu_fence_ops;
>   static inline struct amdgpu_fence *to_amdgpu_fence(struct dma_fence *f)
>   {
>   	struct amdgpu_fence *__f = container_of(f, struct amdgpu_fence, base);
> @@ -158,21 +158,22 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f, struct amd
>   	}
>   
>   	seq = ++ring->fence_drv.sync_seq;
> -	if (job != NULL && job->job_run_counter) {
> +	if (job && job->job_run_counter) {
>   		/* reinit seq for resubmitted jobs */
>   		fence->seqno = seq;
> +		set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT, &fence->flags);
>   	} else {
> +		amdgpu_fence_ops.init_flags = 0;
> +		if (job)
> +			set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT,
> +				&amdgpu_fence_ops.init_flags);

That is utterly nonsense. The amdgpu_fence_ops are global and can't be 
modified like that.

Christian.

> +
>   		dma_fence_init(fence, &amdgpu_fence_ops,
>   				&ring->fence_drv.lock,
>   				adev->fence_context + ring->idx,
>   				seq);
>   	}
>   
> -	if (job != NULL) {
> -		/* mark this fence has a parent job */
> -		set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT, &fence->flags);
> -	}
> -
>   	amdgpu_ring_emit_fence(ring, ring->fence_drv.gpu_addr,
>   			       seq, flags | AMDGPU_FENCE_FLAG_INT);
>   	pm_runtime_get_noresume(adev_to_drm(adev)->dev);
> @@ -720,7 +721,7 @@ static void amdgpu_fence_release(struct dma_fence *f)
>   	call_rcu(&f->rcu, amdgpu_fence_free);
>   }
>   
> -static const struct dma_fence_ops amdgpu_fence_ops = {
> +static struct dma_fence_ops amdgpu_fence_ops = {
>   	.get_driver_name = amdgpu_fence_get_driver_name,
>   	.get_timeline_name = amdgpu_fence_get_timeline_name,
>   	.enable_signaling = amdgpu_fence_enable_signaling,