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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Tue, 7 Jun 2022 14:36:02 -0400
Message-ID: <CADnq5_MiHN=iXt4E5AKSixRqMR5bkqwoxXd_KUj02DFtcwhS6w@mail.gmail.com>
Subject: Re: [PATCH 1/1] drm/radeon: Initialize fences array entries in radeon_sa_bo_next_hole
To:     Xiaohui Zhang <xiaohuizhang@ruc.edu.cn>
Cc:     Alex Deucher <alexander.deucher@amd.com>,
        Christian Koenig <christian.koenig@amd.com>,
        xinhui pan <Xinhui.Pan@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
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Precedence: bulk

Applied.  Thanks!

Alex

On Tue, Jun 7, 2022 at 12:04 PM Xiaohui Zhang <xiaohuizhang@ruc.edu.cn> wrote:
>
> 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.
>
> Signed-off-by: Xiaohui Zhang <xiaohuizhang@ruc.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);
> --
> 2.17.1
>