CVE-2023-52504

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