On Wed, Oct 11, 2023 at 09:46:16AM +0200, Peter Zijlstra wrote: > On Wed, Oct 11, 2023 at 09:58:49AM +0300, Kirill A. Shutemov wrote: > > Fei has reported that KASAN triggers during apply_alternatives() on > > 5-level paging machine: > > > > Urgh @ KASAN splat, can't we summarize that? What about this? 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 ? text_poke_early trace_hardirqs_on ? __asan_load4 text_poke_early apply_alternatives ... Is it enough details or I overdid summarization? > > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c > > index 517ee01503be..b4cc4d7c0825 100644 > > --- a/arch/x86/kernel/alternative.c > > +++ b/arch/x86/kernel/alternative.c > > @@ -403,6 +403,17 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, > > u8 insn_buff[MAX_PATCH_LEN]; > > > > DPRINTK(ALT, "alt table %px, -> %px", start, end); > > + > > + /* > > + * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using > > + * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. > > + * During the process, KASAN becomes confused and triggers > > because of partial LA57 convertion .. > > > + * a false-positive out-of-bound report. > > + * > > + * Disable KASAN until the patching is complete. > > + */ > > + kasan_disable_current(); > > + > > /* /* * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. * During the process, KASAN becomes confused seeing partial LA57 * conversion and triggers a false-positive out-of-bound report. * * Disable KASAN until the patching is complete. */ Looks good? If yes, I will submit v3 with your Ack. -- Kiryl Shutsemau / Kirill A. Shutemov
