Hi Chris!
On 12/26/24 00:09, Chris Bainbridge wrote:
Commit c6a837088bed ("drm/amd/display: Fetch the EDID from _DDC if
available for eDP") added function dm_helpers_probe_acpi_edid, which
fetches the EDID from the BIOS by calling acpi_video_get_edid.
acpi_video_get_edid returns a pointer to the EDID, but this pointer does
not originate from kmalloc - it is actually the internal "pointer" field
from an acpi_buffer struct (which did come from kmalloc).
dm_helpers_probe_acpi_edid then attempts to kfree the EDID pointer,
resulting in memory corruption which leads to random, intermittent
crashes (e.g. 4% of boots will fail with some Oops).
Fix this by allocating a new array (which can be safely freed) for the
EDID data in acpi_video_get_edid, and correctly freeing the acpi_buffer.
Hmm, maybe I'm missing something here. But shouldn't it suffice to just
remove the kfree call in dm_helpers_probe_acpi_edid()?
With best wishes,
Tobias
The only other caller of acpi_video_get_edid is nouveau_acpi_edid:
remove the extraneous kmemdup here as the EDID data is now copied in
acpi_video_get_edid.
Signed-off-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx>
Fixes: c6a837088bed ("drm/amd/display: Fetch the EDID from _DDC if available for eDP")
---
drivers/acpi/acpi_video.c | 3 ++-
drivers/gpu/drm/nouveau/nouveau_acpi.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 8274a17872ed..151d1d534264 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -1485,7 +1485,8 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id,
if (!length)
continue;
- *edid = buffer->buffer.pointer;
+ *edid = kmemdup(buffer->buffer.pointer, length, GFP_KERNEL);
+ kfree(buffer);
return length;
}
diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index 8f0c69aad248..21b56cc7605c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -384,7 +384,7 @@ nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector)
if (ret < 0)
return NULL;
- return kmemdup(edid, EDID_LENGTH, GFP_KERNEL);
+ return edid;
}
bool nouveau_acpi_video_backlight_use_native(void)
