Re: [PATCH v3 10/10] ACPI: extlog: Validate elog record length before walking sections

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

On Fri, Jul 17, 2026 at 09:16:47AM -0700, Dave Jiang wrote:
> sashiko-bot flagged a missing bounds check on data_length that allows
> an out-of-bounds read of elog_buf.
> 
> extlog_print() copies a fixed ELOG_ENTRY_LEN (4096) bytes from the elog
> record into elog_buf, then walks the sections using the
> firmware-controlled data_length. Nothing checks that data_length stays
> within the buffer, so a malformed record can walk the section pointer
> past elog_buf and read adjacent memory.
> 
> Unlike the GHES paths, extlog never calls cper_estatus_check(). Reject a
> record whose length exceeds ELOG_ENTRY_LEN and run cper_estatus_check()
> before walking the sections.
> 
> A malformed record is now dropped with NOTIFY_DONE without setting
> MCE_HANDLED_EXTLOG, reflecting that extlog did not consume it.
> 
> Reported-by: sashiko-bot@kernel.org
> Closes: https://sashiko.dev/#/patchset/20260714231835.303081-1-dave.jiang@intel.com?part=6
> Fixes: f6ec01da40e4 ("ACPI: extlog: Handle multiple records")
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>

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