[Intel-xe] [PATCH] drm/xe: Fix memory use after free

[Matt Roper]

On Fri, Apr 07, 2023 at 02:12:31PM -0700, Niranjana Vishwanathapura wrote:
> The wait_event_timeout() on g2h_fence.wq which is declared on
> stack can return before the wake_up() gets called, resulting in a
> stack out of bound access when wake_up() accesses the g2h_fene.wq.
> 
> Do not declare g2h_fence related wait_queue_head_t on stack.
> 
> Fixes the below KASAN BUG and associated kernel crashes.
> 
> BUG: KASAN: stack-out-of-bounds in do_raw_spin_lock+0x6f/0x1e0
> Read of size 4 at addr ffff88826252f4ac by task kworker/u128:5/467
> 
> CPU: 25 PID: 467 Comm: kworker/u128:5 Tainted: G  U 6.3.0-rc4-xe #1
> Workqueue: events_unbound g2h_worker_func [xe]
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x64/0xb0
>  print_report+0xc2/0x600
>  kasan_report+0x96/0xc0
>  do_raw_spin_lock+0x6f/0x1e0
>  _raw_spin_lock_irqsave+0x47/0x60
>  __wake_up_common_lock+0xc0/0x150
>  dequeue_one_g2h+0x20f/0x6a0 [xe]
>  g2h_worker_func+0xa9/0x180 [xe]
>  process_one_work+0x527/0x990
>  worker_thread+0x2d1/0x640
>  kthread+0x174/0x1b0
>  ret_from_fork+0x29/0x50
>  </TASK>
> 
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>

Tested-by: Matt Roper <matthew.d.roper at intel.com>

Seems to solve the occasional NULL derefs I was seeing on ~2.5% of my
driver load attempts.


Matt

> ---
>  drivers/gpu/drm/xe/xe_guc_ct.c       | 7 +++----
>  drivers/gpu/drm/xe/xe_guc_ct_types.h | 2 ++
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 5e00b75d3ca2..9055ff133a7c 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -23,7 +23,6 @@
>  
>  /* Used when a CT send wants to block and / or receive data */
>  struct g2h_fence {
> -	wait_queue_head_t wq;
>  	u32 *response_buffer;
>  	u32 seqno;
>  	u16 response_len;
> @@ -142,6 +141,7 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
>  	ct->fence_context = dma_fence_context_alloc(1);
>  	INIT_WORK(&ct->g2h_worker, g2h_worker_func);
>  	init_waitqueue_head(&ct->wq);
> +	init_waitqueue_head(&ct->g2h_fence_wq);
>  
>  	primelockdep(ct);
>  
> @@ -484,7 +484,6 @@ static int __guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action,
>  			void *ptr;
>  
>  			g2h_fence->seqno = (ct->fence_seqno++ & 0xffff);
> -			init_waitqueue_head(&g2h_fence->wq);
>  			ptr = xa_store(&ct->fence_lookup,
>  				       g2h_fence->seqno,
>  				       g2h_fence, GFP_ATOMIC);
> @@ -709,7 +708,7 @@ static int guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
>  		return ret;
>  	}
>  
> -	ret = wait_event_timeout(g2h_fence.wq, g2h_fence.done, HZ);
> +	ret = wait_event_timeout(ct->g2h_fence_wq, g2h_fence.done, HZ);
>  	if (!ret) {
>  		drm_err(&xe->drm, "Timed out wait for G2H, fence %u, action %04x",
>  			g2h_fence.seqno, action[0]);
> @@ -801,7 +800,7 @@ static int parse_g2h_response(struct xe_guc_ct *ct, u32 *msg, u32 len)
>  	g2h_fence->done = true;
>  	smp_mb();
>  
> -	wake_up(&g2h_fence->wq);
> +	wake_up_all(&ct->g2h_fence_wq);
>  
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct_types.h b/drivers/gpu/drm/xe/xe_guc_ct_types.h
> index e0f9063e9b65..fd27dacf00c5 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct_types.h
> +++ b/drivers/gpu/drm/xe/xe_guc_ct_types.h
> @@ -74,6 +74,8 @@ struct xe_guc_ct {
>  	struct xarray fence_lookup;
>  	/** @wq: wait queue used for reliable CT sends and freeing G2H credits */
>  	wait_queue_head_t wq;
> +	/** @g2h_fence_wq: wait queue used for G2H fencing */
> +	wait_queue_head_t g2h_fence_wq;
>  #ifdef XE_GUC_CT_SELFTEST
>  	/** @suppress_irq_handler: force flow control to sender */
>  	bool suppress_irq_handler;
> -- 
> 2.21.0.rc0.32.g243a4c7e27
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation