Am 04.07.26 um 20:43 schrieb [email protected]:
Thank you for your contribution! Sashiko AI review found 2 potential issue(s)
to consider:
New issues:
- [High] NULL pointer dereference when enabling CRTC without a primary plane
framebuffer.
False positive here. Calling drm_atomic_helper_check_primary_plane()
from the CRTC's atomic check makes it impossible to enable the CRTC
without a primary plane.
Pre-existing issues:
- [High] Unsafe direct access of global plane and CRTC state pointers in atomic
commit callbacks.
--
commit 6344532446cab68117e44660f110ef0c8aec15d7
Author: Ze Huang <[email protected]>
drm/arcpgu: replace struct drm_simple_display_pipe with regular atomic helpers
This commit replaces drm_simple_display_pipe with regular atomic helpers.
It instantiates the plane, CRTC, and encoder directly, wiring them up with
standard atomic helpers to remove the dependency on the simple-KMS interface.
diff --git a/drivers/gpu/drm/tiny/arcpgu.c b/drivers/gpu/drm/tiny/arcpgu.c
index c93d61ac0bb75..375cdb79e4e89 100644
--- a/drivers/gpu/drm/tiny/arcpgu.c
+++ b/drivers/gpu/drm/tiny/arcpgu.c
[ ... ]
@@ -117,7 +117,7 @@ static const u32 arc_pgu_supported_formats[] = {
static void arc_pgu_set_pxl_fmt(struct arcpgu_drm_private *arcpgu)
{
- const struct drm_framebuffer *fb = arcpgu->pipe.plane.state->fb;
+ const struct drm_framebuffer *fb = arcpgu->plane.state->fb;
[Severity: High]
This isn't a bug introduced by this patch, but does reading the global
plane->state pointer here instead of using the state passed via the
drm_atomic_commit parameter cause issues during non-blocking atomic commits?
If multiple non-blocking commits are queued rapidly, the global pointers
advance to the newest state. When the first commit's commit_tail finally
executes, reading plane->state directly instead of extracting the specific
commit's state could cause the older commit to program the hardware using a
future commit's state.
[Severity: High]
Can this dereference a NULL pointer if the CRTC is enabled without a primary
plane framebuffer?
The transition from drm_simple_display_pipe to generic atomic helpers removed
the underlying protection that previously prevented the CRTC from enabling
without a valid framebuffer. If userspace performs an atomic commit that
enables the CRTC but sets the primary plane's framebuffer to 0 (NULL),
drm_atomic_helper_check_crtc_primary_plane verifies the plane is attached but
does not enforce plane_state->fb != NULL.
This would allow the commit to proceed to arcpgu_crtc_helper_atomic_enable(),
which calls arc_pgu_mode_set(), and then arc_pgu_set_pxl_fmt(), blindly
dereferencing fb->format->format here.
uint32_t pixel_format = fb->format->format;
u32 format = DRM_FORMAT_INVALID;
int i;
[ ... ]
@@ -155,7 +155,7 @@ static enum drm_mode_status arc_pgu_mode_valid(struct
drm_simple_display_pipe *p
static void arc_pgu_mode_set(struct arcpgu_drm_private *arcpgu)
{
- struct drm_display_mode *m = &arcpgu->pipe.crtc.state->adjusted_mode;
+ struct drm_display_mode *m = &arcpgu->crtc.state->adjusted_mode;
[Severity: High]
This is a pre-existing issue, but could reading the global crtc->state pointer
directly cause hardware state corruption or frame tearing?
Similar to the plane state issue above, if rapid non-blocking atomic commits
are generated, arc_pgu_mode_set() might read from the newest global state
rather than the specific commit's state object.
u32 val;
arc_pgu_write(arcpgu, ARCPGU_REG_FMT,
[ ... ]
@@ -218,35 +218,106 @@ static void arc_pgu_disable(struct
drm_simple_display_pipe *pipe)
~ARCPGU_CTRL_ENABLE_MASK);
}
-static void arc_pgu_update(struct drm_simple_display_pipe *pipe,
- struct drm_plane_state *state)
+static void arcpgu_plane_helper_atomic_update(struct drm_plane *plane,
+ struct drm_atomic_commit *state)
{
struct arcpgu_drm_private *arcpgu;
struct drm_gem_dma_object *gem;
- if (!pipe->plane.state->fb)
+ if (!plane->state->fb)
[Severity: High]
This is a pre-existing issue, but does arcpgu_plane_helper_atomic_update()
safely handle non-blocking atomic commits when reading plane->state->fb
directly?
Reading the global plane->state pointer instead of extracting the new plane
state from the drm_atomic_commit parameter could result in the same race
condition during asynchronous commit_tail execution.
return;
- arcpgu = pipe_to_arcpgu_priv(pipe);
- gem = drm_fb_dma_get_gem_obj(pipe->plane.state->fb, 0);
+ arcpgu = dev_to_arcpgu(plane->dev);
+ gem = drm_fb_dma_get_gem_obj(plane->state->fb, 0);
arc_pgu_write(arcpgu, ARCPGU_REG_BUF0_ADDR, gem->dma_addr);
}
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
