CVE-2023-52504

In the Linux kernel, the following vulnerability has been resolved:
x86/alternatives: Disable KASAN in apply_alternatives() Fei has reported
that KASAN triggers during apply_alternatives() on a 5-level paging
machine: BUG: KASAN: out-of-bounds in rcu_is_watching() Read of size 4 at
addr ff110003ee6419a0 by task swapper/0/0 … __asan_load4()
rcu_is_watching() trace_hardirqs_on() text_poke_early()
apply_alternatives() … On machines with 5-level paging,
cpu_feature_enabled(X86_FEATURE_LA57) gets patched. It includes KASAN code,
where KASAN_SHADOW_START depends on __VIRTUAL_MASK_SHIFT, which is defined
with cpu_feature_enabled(). KASAN gets confused when apply_alternatives()
patches the KASAN_SHADOW_START users. A test patch that makes
KASAN_SHADOW_START static, by replacing __VIRTUAL_MASK_SHIFT with 56, works
around the issue. Fix it for real by disabling KASAN while the kernel is
patching alternatives. [ mingo: updated the changelog ]