CVE-2026-43266

In the Linux kernel, the following vulnerability has been resolved:

EFI/CPER: don't go past the ARM processor CPER record buffer

There's a logic inside GHES/CPER to detect if the section_length is too small, but it doesn't detect if it is too big.

Currently, if the firmware receives an ARM processor CPER record stating that a section length is big, kernel will blindly trust sectionlength, producing a very long dump. For instance, a 67 bytes record with ERRINFO_NUM set 46198 and section length set to 854918320 would dump a lot of data going a way past the firmware memory-mapped area.

Fix it by adding a logic to prevent it to go past the buffer if ERRINFONUM is too big, making it report instead:

[Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 1
[Hardware Error]: event severity: recoverable
[Hardware Error]:  Error 0, type: recoverable
[Hardware Error]:   section_type: ARM processor error
[Hardware Error]:   MIDR: 0xff304b2f8476870a
[Hardware Error]:   section length: 854918320, CPER size: 67
[Hardware Error]:   section length is too big
[Hardware Error]:   firmware-generated error record is incorrect
[Hardware Error]:   ERR_INFO_NUM is 46198

[ rjw: Subject and changelog tweaks ]