lwn.git/drivers/gpu/drm/amd/display/dc, branch master

drm/amd/display: Validate payload length and link_index in dc_process_dmub_aux_transfer_async

2026-05-19T16:13:56+00:00

[Why&How] dc_process_dmub_aux_transfer_async() copies payload->length bytes into a 16-byte stack buffer (dpaux.data[16]) guarded only by an ASSERT(), which is a no-op in release builds. If a caller ever passes length > 16 this results in a stack buffer overflow via memcpy. Additionally, link_index is used to dereference dc->links[] without bounds checking against dc->link_count, risking an out-of-bounds access. Replace the ASSERT with a hard runtime check that returns false when payload->length exceeds the destination buffer size, and add a bounds check for link_index before it is used. Assisted-by: GitHub Copilot:Claude claude-4-opus Reviewed-by: Alex Hung Signed-off-by: Harry Wentland Signed-off-by: Ivan Lipski Tested-by: Dan Wheeler Signed-off-by: Alex Deucher (cherry picked from commit ba4caa9fecdf7a38f98c878ad05a8a64148b6881) Cc: stable@vger.kernel.org

drm/amd/display: Validate GPIO pin LUT table size before iterating

2026-05-19T16:13:29+00:00

[Why&How] The GPIO pin table parsers in get_gpio_i2c_info() and bios_parser_get_gpio_pin_info() derive an element count from the VBIOS table_header.structuresize field, then iterate over gpio_pin[] entries. However, GET_IMAGE() only validates that the table header itself fits within the BIOS image. If the VBIOS reports a structuresize larger than the actual mapped data, the loop reads past the end of the BIOS image, causing an out-of-bounds read. Fix this by calling bios_get_image() to validate that the full claimed structuresize is accessible within the BIOS image before entering the loop in both functions. Assisted-by: GitHub Copilot:claude-opus-4-6 Reviewed-by: Alex Hung Signed-off-by: Harry Wentland Signed-off-by: Ivan Lipski Tested-by: Dan Wheeler Signed-off-by: Alex Deucher (cherry picked from commit ba5e95b43b773ae1bf1f66ee6b31eb774e65afe3) Cc: stable@vger.kernel.org

drm/amd/display: Fix integer overflow in bios_get_image()

2026-05-19T16:13:07+00:00

[Why&How] The bounds check in bios_get_image() computes 'offset + size' using unsigned 32-bit arithmetic before comparing against bios_size. If a VBIOS image contains a near-UINT32_MAX offset the addition wraps to a small value, the comparison passes, and the function returns a wild pointer past the VBIOS mapping. Additionally, the comparison uses '<' (strict), which incorrectly rejects the valid exact-fit case where offset + size == bios_size. Fix both issues by restructuring the check to avoid the addition entirely: first reject if offset alone exceeds bios_size, then check size against the remaining space (bios_size - offset). This eliminates the overflow and correctly permits exact-fit accesses. Assisted-by: GitHub Copilot:claude-opus-4.6 Reviewed-by: Alex Hung Signed-off-by: Harry Wentland Signed-off-by: Ivan Lipski Tested-by: Dan Wheeler Signed-off-by: Alex Deucher (cherry picked from commit d40fb392af659c4a02b560319f226842f6ec1a95) Cc: stable@vger.kernel.org

drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED

2026-05-11T21:53:31+00:00

[Why] dcn32_validate_bandwidth() wraps dcn32_internal_validate_bw() with DC_FP_START()/DC_FP_END(). In x86 non-RT, DC_FP_START takes fpregs_lock(), which disables local softirqs. The DML1 path through dcn32_enable_phantom_plane() calls kvzalloc() to allocate ~335 KiB for dc_plane_state. This triggers the vmalloc path, which calls BUG_ON(in_interrupt()) because it's invoked within the FPU-enabled (softirq disabled) region, leading to a kernel crash. [How] Wrap the dc_state_create_phantom_plane() call with the DC_RUN_WITH_PREEMPTION_ENABLED() macro to allow preemption during this memory allocation. Fixes: 235c67634230 ("drm/amd/display: add DCN32/321 specific files for Display Core") Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/4470 Reviewed-by: Aurabindo Pillai Signed-off-by: Mikhail Gavrilov Signed-off-by: James Lin Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 885ccbef7b94a8b38f69c4211c679021aa27ad11) Cc: stable@vger.kernel.org

drm/amd/display: Read EDID from VBIOS embedded panel info

2026-04-29T14:41:40+00:00

Some board manufacturers hardcode the EDID for the embedded panel in the VBIOS. This EDID should be used when the panel doesn't have a DDC. For reference, see the legacy non-DC display code: amdgpu_atombios_encoder_get_lcd_info() This is necessary to support embedded connectors without DDC. Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192 Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher (cherry picked from commit eb105e63b474c11ef6a84a1c6b18100d851ff364)

drm/amd/display: Allow constructing DCE8 link encoder without DDC

2026-04-29T14:41:34+00:00

When the DDC channel ID is set to CHANNEL_ID_UNKNOWN, pass NULL to the AUX regs array. This is necessary to support embedded connectors without DDC. Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192 Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher (cherry picked from commit 155baf3038c1af50b602723022ed869b38e86a99)

drm/amd/display: Allow constructing DCE6 link encoder without DDC

2026-04-29T14:41:28+00:00

When the DDC channel ID is set to CHANNEL_ID_UNKNOWN, pass NULL to the AUX regs array. This is necessary to support embedded connectors without DDC. Fixes: 7c15fd86aaec ("drm/amd/display: dc/dce: add initial DCE6 support (v10)") Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192 Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher (cherry picked from commit 38a70e50b22a188ff601740d64dd75f46213121f)

drm/amd/display: Allow DCE link encoder without AUX registers

2026-04-29T14:41:22+00:00

Allow constructing the DCE link encoder without DDC, which means the AUX registers array will be NULL. This is necessary to support embedded connectors without DDC. Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192 Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher (cherry picked from commit 87f30b101af62590faf6020d106da07efdda199b)

drm/amd/display: Allow embedded connectors without DDC

2026-04-29T14:41:15+00:00

On some laptops, the embedded panel may not have a DDC (display data channel) available. On these, the EDID may be hardcoded in ACPI or the VBIOS. In this case, use GPIO_DDC_LINE_UNKNOWN and don't fail. Fixes: def3488eb0fd ("drm/amd/display: refactor HPD to increase flexibility") Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192 Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher (cherry picked from commit 75b8a6ca0e8bc3ce24572f854e95f8721b321179)

drm/amd/display: Update MCIF_ADDR macro to address IGT DWB regression

2026-04-28T19:45:28+00:00

[Why] A previous warning-fix commit updated type casts in the DCN3 mmhubbub code but missed updating the MCIF_ADDR macro to the correct, fully parenthesized and casted version. This caused a regression during DWB tests, where address values could be misinterpreted, potentially leading to incorrect hardware programming. [How] Updated the MCIF_ADDR macro in dcn30_mmhubbub.c to use the proper parenthesization and type casting, ensuring correct address handling. Removed redundant casts from REG_UPDATE calls for improved clarity and consistency with current coding standards. Fixes: f4cdbb5d5405 ("drm/amd/display: Fix implicit narrowing conversion warnings") Reviewed-by: Clayton King Signed-off-by: Gaghik Khachatrian Signed-off-by: Tom Chung Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 4f251a5e9f2297023b00b7cab606de111931cfa3)