In the Linux kernel, the following vulnerability has been resolved:
arm64: mm: Fix lockless walks with static and dynamic page-table folding
Lina reports random oopsen originating from the fast GUP code when
16K pages are used with 4-level page-tables, the fourth level being
folded at runtime due to lack of LPA2.
In this configuration, the generic implementation of
p4d_offset_lockless() will return a ‘p4d_t *’ corresponding to the
‘pgd_t’ allocated on the stack of the caller, gup_fast_pgd_range().
This is normally fine, but when the fourth level of page-table is folded
at runtime, pud_offset_lockless() will offset from the address of the
‘p4d_t’ to calculate the address of the PUD in the same page-table page.
This results in a stray stack read when the ‘p4d_t’ has been allocated
on the stack and can send the walker into the weeds.
Fix the problem by providing our own definition of p4d_offset_lockless()
when CONFIG_PGTABLE_LEVELS <= 4 which returns the real page-table
pointer rather than the address of the local stack variable.
git.kernel.org/linus/36639013b3462c06ff8e3400a427f775b4fc97f5 (6.11-rc1)
git.kernel.org/stable/c/36639013b3462c06ff8e3400a427f775b4fc97f5
git.kernel.org/stable/c/78672d49d3eebbcda3589f4d6e589caf357c5a59
launchpad.net/bugs/cve/CVE-2024-42293
nvd.nist.gov/vuln/detail/CVE-2024-42293
security-tracker.debian.org/tracker/CVE-2024-42293
www.cve.org/CVERecord?id=CVE-2024-42293