Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
Pre-existing issues: - [High] Allocating a 0-sized firmware payload results in a `ZERO_SIZE_PTR` dereference, causing a kernel crash. - [High] Integer underflow in MMIO count loop causes a massive out-of-bounds read and potential crash. -- commit c888be66e6182bdd47cd31d900f609af76cef7a1 Author: Dibin Moolakadan Subrahmanian <[email protected]> drm/i915/dmc: Prevent fw_size multiplication overflow This commit validates the conversion of the DMC firmware size from dwords to bytes using check_mul_overflow(). This prevents a potential integer overflow when calculating the firmware payload size. Fixes: eb805623d8b1 ("drm/i915/skl: Add support to load SKL CSR firmware.") Cc: [email protected] Assisted-by: Claude-Code:Sonnet-5 Signed-off-by: Dibin Moolakadan Subrahmanian <[email protected]> > diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c > b/drivers/gpu/drm/i915/display/intel_dmc.c > index 051b721a08959..228a1b2967336 100644 > --- a/drivers/gpu/drm/i915/display/intel_dmc.c > +++ b/drivers/gpu/drm/i915/display/intel_dmc.c > @@ -1178,7 +1178,12 @@ static u32 parse_dmc_fw_header(struct intel_dmc *dmc, > rem_size -= header_len_bytes; > > /* fw_size is in dwords, so multiplied by 4 to convert into bytes. */ > - payload_size = dmc_header->fw_size * 4; > + if (check_mul_overflow(dmc_header->fw_size, 4u, &payload_size)) { > + drm_err(display->drm, "DMC fw_size too large (%u dwords)\n", > + dmc_header->fw_size); > + return 0; > + } > + [Severity: High] This is a pre-existing issue, but does this code handle a payload_size of 0 safely? If a firmware file has fw_size == 0, payload_size will be 0. Later in parse_dmc_fw_header() in drivers/gpu/drm/i915/display/intel_dmc.c, this results in: dmc_info->payload = kmalloc(payload_size, GFP_KERNEL); When payload_size is 0, kmalloc() returns ZERO_SIZE_PTR (address 16), not NULL. Then, assert_dmc_loaded() unconditionally reads from the payload pointer: expected = dmc->dmc_info[dmc_id].payload[0]; Can this cause a kernel crash when dereferencing the ZERO_SIZE_PTR? [Severity: High] This isn't a bug introduced by this patch, but does parse_dmc_fw_header() safely handle an mmio_count of 0? In parse_dmc_fw_header() in drivers/gpu/drm/i915/display/intel_dmc.c, the loop for processing mmio entries looks like: for (i = 0; i < mmio_count - 1; i++) { u32 orig_mmiodata[2] = { dmc_info->mmiodata[i], dmc_info->mmiodata[i+1], }; ... If the parsed firmware header has mmio_count == 0, the loop condition underflows to UINT_MAX. Could this cause a massive out-of-bounds read when accessing dmc_info->mmiodata[i]? > if (rem_size < payload_size) > goto error_truncated; > -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2
