| Description: | 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 ]
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