Re: [PATCH] drm/amd/pm: fix double free in si_parse_power_table()

From: Alex Deucher <alexdeucher@gmail.com>
To: Keita Suzuki <keitasuzuki.park@sslab.ics.keio.ac.jp>
Cc: "Lijo Lazar" <lijo.lazar@amd.com>,
	"David Airlie" <airlied@linux.ie>,
	"Maíra Canal" <maira.canal@usp.br>,
	"Pan, Xinhui" <Xinhui.Pan@amd.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	"amd-gfx list" <amd-gfx@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Maling list - DRI developers" <dri-devel@lists.freedesktop.org>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Evan Quan" <evan.quan@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"Hawking Zhang" <Hawking.Zhang@amd.com>
Subject: Re: [PATCH] drm/amd/pm: fix double free in si_parse_power_table()
Date: Tue, 19 Apr 2022 10:38:49 -0400	[thread overview]
Message-ID: <CADnq5_MfjrZvegj-4r4DhRR5FDe6casvfcy54G0tM8PZqbsHeg@mail.gmail.com> (raw)
In-Reply-To: <20220419103721.4080045-1-keitasuzuki.park@sslab.ics.keio.ac.jp>

Applied.  Thanks!

On Tue, Apr 19, 2022 at 8:49 AM Keita Suzuki
<keitasuzuki.park@sslab.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@sslab.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
>