drm/amdgpu: fix a job->pasid access race in gpu recovery

Avoid a possible UAF in GPU recovery due to a race between
the sched timeout callback and the tdr work queue.

The gpu recovery function calls drm_sched_stop() and
later drm_sched_start().  drm_sched_start() restarts
the tdr queue which will eventually free the job.  If
the tdr queue frees the job before time out callback
completes, the job will be freed and we'll get a UAF
when accessing the pasid.  Cache it early to avoid the
UAF.

Example KASAN trace:
[  493.058141] BUG: KASAN: slab-use-after-free in amdgpu_device_gpu_recover+0x968/0x990 [amdgpu]
[  493.067530] Read of size 4 at addr ffff88b0ce3f794c by task kworker/u128:1/323
[  493.074892]
[  493.076485] CPU: 9 UID: 0 PID: 323 Comm: kworker/u128:1 Tainted: G            E       6.16.0-1289896.2.zuul.bf4f11df81c1410bbe901c4373305a31 #1 PREEMPT(voluntary)
[  493.076493] Tainted: [E]=UNSIGNED_MODULE
[  493.076495] Hardware name: TYAN B8021G88V2HR-2T/S8021GM2NR-2T, BIOS V1.03.B10 04/01/2019
[  493.076500] Workqueue: amdgpu-reset-dev drm_sched_job_timedout [gpu_sched]
[  493.076512] Call Trace:
[  493.076515]  <TASK>
[  493.076518]  dump_stack_lvl+0x64/0x80
[  493.076529]  print_report+0xce/0x630
[  493.076536]  ? _raw_spin_lock_irqsave+0x86/0xd0
[  493.076541]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
[  493.076545]  ? amdgpu_device_gpu_recover+0x968/0x990 [amdgpu]
[  493.077253]  kasan_report+0xb8/0xf0
[  493.077258]  ? amdgpu_device_gpu_recover+0x968/0x990 [amdgpu]
[  493.077965]  amdgpu_device_gpu_recover+0x968/0x990 [amdgpu]
[  493.078672]  ? __pfx_amdgpu_device_gpu_recover+0x10/0x10 [amdgpu]
[  493.079378]  ? amdgpu_coredump+0x1fd/0x4c0 [amdgpu]
[  493.080111]  amdgpu_job_timedout+0x642/0x1400 [amdgpu]
[  493.080903]  ? pick_task_fair+0x24e/0x330
[  493.080910]  ? __pfx_amdgpu_job_timedout+0x10/0x10 [amdgpu]
[  493.081702]  ? _raw_spin_lock+0x75/0xc0
[  493.081708]  ? __pfx__raw_spin_lock+0x10/0x10
[  493.081712]  drm_sched_job_timedout+0x1b0/0x4b0 [gpu_sched]
[  493.081721]  ? __pfx__raw_spin_lock_irq+0x10/0x10
[  493.081725]  process_one_work+0x679/0xff0
[  493.081732]  worker_thread+0x6ce/0xfd0
[  493.081736]  ? __pfx_worker_thread+0x10/0x10
[  493.081739]  kthread+0x376/0x730
[  493.081744]  ? __pfx_kthread+0x10/0x10
[  493.081748]  ? __pfx__raw_spin_lock_irq+0x10/0x10
[  493.081751]  ? __pfx_kthread+0x10/0x10
[  493.081755]  ret_from_fork+0x247/0x330
[  493.081761]  ? __pfx_kthread+0x10/0x10
[  493.081764]  ret_from_fork_asm+0x1a/0x30
[  493.081771]  </TASK>

Fixes: a72002c ("drm/amdgpu: Make use of drm_wedge_task_info")
Link: HansKristian-Work/vkd3d-proton#2670
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Suggested-by: Matthew Brost <[email protected]>
Reviewed-by: Srinivasan Shanmugam <[email protected]>
Reviewed-by: Lijo Lazar <[email protected]>
Reviewed-by: Christian König <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: alexdeucher

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -6620,6 +6620,8 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 	struct amdgpu_hive_info *hive = NULL;
 	int r = 0;
 	bool need_emergency_restart = false;
+	/* save the pasid here as the job may be freed before the end of the reset */
+	int pasid = job ? job->pasid : -EINVAL;
 
 	/*
 	 * If it reaches here because of hang/timeout and a RAS error is
@@ -6720,8 +6722,12 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 	if (!r) {
 		struct amdgpu_task_info *ti = NULL;
 
-		if (job)
-			ti = amdgpu_vm_get_task_info_pasid(adev, job->pasid);
+		/*
+		 * The job may already be freed at this point via the sched tdr workqueue so
+		 * use the cached pasid.
+		 */
+		if (pasid >= 0)
+			ti = amdgpu_vm_get_task_info_pasid(adev, pasid);
 
 		drm_dev_wedged_event(adev_to_drm(adev), DRM_WEDGE_RECOVERY_NONE,
 				     ti ? &ti->task : NULL);