[PATCH] drm/amdgpu: Move the mutex_lock to protect the return status of securedisplay command buffer

[Alex Deucher]

On Tue, Oct 25, 2022 at 4:00 AM Alan Liu <HaoPing.Liu at amd.com> wrote:
>
> [Why]
> Before we call psp_securedisplay_invoke(), we call
> psp_prep_securedisplay_cmd_buf() to prepare and initialize the command
> buffer.
>
> However, we didn't use the mutex_lock to protect the status of command
> buffer. So when multiple threads are using the command buffer, after
> thread A return from psp_securedisplay_invoke() and the command buffer
> status is set to SUCCESS, another thread B may call
> psp_prep_securedisplay_cmd_buf() and initialize the status to FAILURE
> again, and cause Thread A to get a failure return status.
>
> [How]
> Move the mutex_lock out of psp_securedisplay_invoke() to its caller to
> cover psp_prep_securedisplay_cmd_buf() and the code checking the return
> status of command buffer.
>
> Signed-off-by: Alan Liu <HaoPing.Liu at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c               | 9 +++++----
>  drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c     | 4 ++++
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c | 4 ++++
>  3 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c
> index effa7df3ddbf..7bbf869f4f0d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c
> @@ -1938,10 +1938,15 @@ static int psp_securedisplay_initialize(struct psp_context *psp)
>         } else
>                 return ret;
>
> +       mutex_lock(&psp->securedisplay_context.mutex);
> +
>         psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
>                         TA_SECUREDISPLAY_COMMAND__QUERY_TA);
>
>         ret = psp_securedisplay_invoke(psp, TA_SECUREDISPLAY_COMMAND__QUERY_TA);
> +
> +       mutex_unlock(&psp->securedisplay_context.mutex);
> +
>         if (ret) {
>                 psp_securedisplay_terminate(psp);
>                 /* free securedisplay shared memory */
> @@ -1990,12 +1995,8 @@ int psp_securedisplay_invoke(struct psp_context *psp, uint32_t ta_cmd_id)
>             ta_cmd_id != TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC)
>                 return -EINVAL;
>
> -       mutex_lock(&psp->securedisplay_context.mutex);
> -
>         ret = psp_ta_invoke(psp, ta_cmd_id, &psp->securedisplay_context.context);
>
> -       mutex_unlock(&psp->securedisplay_context.mutex);
> -
>         return ret;
>  }
>  /* SECUREDISPLAY end */
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> index cc7597a15fe9..2c1d82fc4c34 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> @@ -121,6 +121,7 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct file *f, const char __u
>
>         switch (op) {
>         case 1:
> +               mutex_lock(&psp->securedisplay_context.mutex);
>                 psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
>                         TA_SECUREDISPLAY_COMMAND__QUERY_TA);
>                 ret = psp_securedisplay_invoke(psp, TA_SECUREDISPLAY_COMMAND__QUERY_TA);
> @@ -131,8 +132,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct file *f, const char __u
>                         else
>                                 psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
>                 }
> +               mutex_unlock(&psp->securedisplay_context.mutex);
>                 break;
>         case 2:
> +               mutex_lock(&psp->securedisplay_context.mutex);
>                 psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
>                         TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
>                 securedisplay_cmd->securedisplay_in_message.send_roi_crc.phy_id = phy_id;
> @@ -146,6 +149,7 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct file *f, const char __u
>                                 psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
>                         }
>                 }
> +               mutex_unlock(&psp->securedisplay_context.mutex);
>                 break;
>         default:
>                 dev_err(adev->dev, "Invalid input: %s\n", str);
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
> index 8a441a22c46e..515352ba788e 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
> @@ -123,6 +123,8 @@ static void amdgpu_dm_crtc_notify_ta_to_read(struct work_struct *work)
>         phy_id = crc_rd_wrk->phy_inst;
>         spin_unlock_irq(&crc_rd_wrk->crc_rd_work_lock);
>
> +       mutex_lock(&psp->securedisplay_context.mutex);
> +
>         psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
>                                                 TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
>         securedisplay_cmd->securedisplay_in_message.send_roi_crc.phy_id =
> @@ -133,6 +135,8 @@ static void amdgpu_dm_crtc_notify_ta_to_read(struct work_struct *work)
>                         psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
>                 }
>         }
> +
> +       mutex_unlock(&psp->securedisplay_context.mutex);
>  }
>
>  bool amdgpu_dm_crc_window_is_activated(struct drm_crtc *crtc)
> --
> 2.25.1
>