linux-kernel - Re: [PATCH] drm/amd/pm: fix double free in si_parse_power

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Date:   Tue, 19 Apr 2022 10:38:49 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Keita Suzuki <keitasuzuki.park@...ab.ics.keio.ac.jp>
Cc:     Lijo Lazar <lijo.lazar@....com>, David Airlie <airlied@...ux.ie>,
        Maíra Canal <maira.canal@....br>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>, Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Evan Quan <evan.quan@....com>,
        Christian König <christian.koenig@....com>,
        Hawking Zhang <Hawking.Zhang@....com>
Subject: Re: [PATCH] drm/amd/pm: fix double free in si_parse_power_table()

Applied.  Thanks!

On Tue, Apr 19, 2022 at 8:49 AM Keita Suzuki
<keitasuzuki.park@...ab.ics.keio.ac.jp> wrote:
>
> In function si_parse_power_table(), array adev->pm.dpm.ps and its member
> is allocated. If the allocation of each member fails, the array itself
> is freed and returned with an error code. However, the array is later
> freed again in si_dpm_fini() function which is called when the function
> returns an error.
>
> This leads to potential double free of the array adev->pm.dpm.ps, as
> well as leak of its array members, since the members are not freed in
> the allocation function and the array is not nulled when freed.
> In addition adev->pm.dpm.num_ps, which keeps track of the allocated
> array member, is not updated until the member allocation is
> successfully finished, this could also lead to either use after free,
> or uninitialized variable access in si_dpm_fini().
>
> Fix this by postponing the free of the array until si_dpm_fini() and
> increment adev->pm.dpm.num_ps everytime the array member is allocated.
>
> Signed-off-by: Keita Suzuki <keitasuzuki.park@...ab.ics.keio.ac.jp>
> ---
>  drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> index caae54487f9c..079888229485 100644
> --- a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> +++ b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> @@ -7331,17 +7331,15 @@ static int si_parse_power_table(struct amdgpu_device *adev)
>         if (!adev->pm.dpm.ps)
>                 return -ENOMEM;
>         power_state_offset = (u8 *)state_array->states;
> -       for (i = 0; i < state_array->ucNumEntries; i++) {
> +       for (adev->pm.dpm.num_ps = 0, i = 0; i < state_array->ucNumEntries; i++) {
>                 u8 *idx;
>                 power_state = (union pplib_power_state *)power_state_offset;
>                 non_clock_array_index = power_state->v2.nonClockInfoIndex;
>                 non_clock_info = (struct _ATOM_PPLIB_NONCLOCK_INFO *)
>                         &non_clock_info_array->nonClockInfo[non_clock_array_index];
>                 ps = kzalloc(sizeof(struct  si_ps), GFP_KERNEL);
> -               if (ps == NULL) {
> -                       kfree(adev->pm.dpm.ps);
> +               if (ps == NULL)
>                         return -ENOMEM;
> -               }
>                 adev->pm.dpm.ps[i].ps_priv = ps;
>                 si_parse_pplib_non_clock_info(adev, &adev->pm.dpm.ps[i],
>                                               non_clock_info,
> @@ -7363,8 +7361,8 @@ static int si_parse_power_table(struct amdgpu_device *adev)
>                         k++;
>                 }
>                 power_state_offset += 2 + power_state->v2.ucNumDPMLevels;
> +               adev->pm.dpm.num_ps++;
>         }
> -       adev->pm.dpm.num_ps = state_array->ucNumEntries;
>
>         /* fill in the vce power states */
>         for (i = 0; i < adev->pm.dpm.num_of_vce_states; i++) {
> --
> 2.25.1
>