linux-kernel - Re: [PATCH 1/1] drm/radeon: Initialize fences array entries in radeon_sa_bo_next

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Message-ID: <b2bfdb5e-25d7-22d8-1788-ba34256e7664@amd.com>
Date:   Wed, 8 Jun 2022 10:35:13 +0200
From:   Christian König <christian.koenig@....com>
To:     Xiaohui Zhang <xiaohuizhang@....edu.cn>,
        Alex Deucher <alexander.deucher@....com>, Xinhui.Pan@....com,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] drm/radeon: Initialize fences array entries in
 radeon_sa_bo_next_hole

Am 07.06.22 um 17:19 schrieb Xiaohui Zhang:
> Similar to the handling of amdgpu_sa_bo_next_hole in commit 6a15f3ff19a8
> ("drm/amdgpu: Initialize fences array entries in amdgpu_sa_bo_next_hole"),
> we thought a patch might be needed here as well.
>
> The entries were only initialized once in radeon_sa_bo_new. If a fence
> wasn't signalled yet in the first radeon_sa_bo_next_hole call, but then
> got signalled before a later radeon_sa_bo_next_hole call, it could
> destroy the fence but leave its pointer in the array, resulting in
> use-after-free in radeon_sa_bo_new.

I would rather like to see the sub allocator moved into a common drm helper.

Regards,
Christian.

>
> Signed-off-by: Xiaohui Zhang <xiaohuizhang@....edu.cn>
> ---
>   drivers/gpu/drm/radeon/radeon_sa.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_sa.c b/drivers/gpu/drm/radeon/radeon_sa.c
> index 310c322c7112..0981948bd9ed 100644
> --- a/drivers/gpu/drm/radeon/radeon_sa.c
> +++ b/drivers/gpu/drm/radeon/radeon_sa.c
> @@ -267,6 +267,8 @@ static bool radeon_sa_bo_next_hole(struct radeon_sa_manager *sa_manager,
>   	for (i = 0; i < RADEON_NUM_RINGS; ++i) {
>   		struct radeon_sa_bo *sa_bo;
>   
> +		fences[i] = NULL;
> +
>   		if (list_empty(&sa_manager->flist[i])) {
>   			continue;
>   		}
> @@ -332,10 +334,8 @@ int radeon_sa_bo_new(struct radeon_device *rdev,
>   
>   	spin_lock(&sa_manager->wq.lock);
>   	do {
> -		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
> -			fences[i] = NULL;
> +		for (i = 0; i < RADEON_NUM_RINGS; ++i)
>   			tries[i] = 0;
> -		}
>   
>   		do {
>   			radeon_sa_bo_try_free(sa_manager);