Re: [PATCH v3 02/10] efi/cper: Reject CPER records with an out-of-range error_data_length

[Alison Schofield <alison.schofield@intel.com>]

On Fri, Jul 17, 2026 at 09:16:39AM -0700, Dave Jiang wrote:
> sashiko-bot flagged that the "len < sizeof(*rec)" guard added in this
> series can be bypassed by an integer overflow in the shared length check.
> 
> cper_estatus_check() bounds firmware CPER data before the section
> handlers in ghes_do_proc() run. It sizes each section with
> acpi_hest_get_record_size(), which adds the firmware-controlled u32
> error_data_length to the header size using signed int helpers in
> <acpi/ghes.h>. A value like 0xffffffb9 sign-converts to a negative
> number, wraps the record size small, and slips past the
> "record_size > data_len" check. A section handler then copies a
> fixed-size payload out of it and reads past the record.
> 
> Reject a section whose error_data_length is negative once sign-converted
> or larger than the remaining data, before the size arithmetic runs.
> 
> Reported-by: sashiko-bot@kernel.org
> Closes: https://sashiko.dev/#/patchset/20260714231835.303081-1-dave.jiang@intel.com?part=1
> Fixes: 45b14a4ffcc1 ("efi: cper: Fix possible out-of-bounds access")
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Reviewed-by: Alison Schofield <alison.schofield@intel.com>