On Thu, Jul 25, 2019 at 7:55 AM Daniel Axtens <dja@xxxxxxxxxx> wrote: > > In the case where KASAN directly allocates memory to back vmalloc > space, don't map the early shadow page over it. > > Not mapping the early shadow page over the whole shadow space means > that there are some pgds that are not populated on boot. Allow the > vmalloc fault handler to also fault in vmalloc shadow as needed. > > Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx> Would it make things simpler if we pre-populate the top level page tables for the whole vmalloc region? That would be (16<<40)/4096/512/512*8 = 131072 bytes? The check in vmalloc_fault in not really a big burden, so I am not sure. Just brining as an option. Acked-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > --- > arch/x86/Kconfig | 1 + > arch/x86/mm/fault.c | 13 +++++++++++++ > arch/x86/mm/kasan_init_64.c | 10 ++++++++++ > 3 files changed, 24 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 222855cc0158..40562cc3771f 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -134,6 +134,7 @@ config X86 > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_JUMP_LABEL_RELATIVE > select HAVE_ARCH_KASAN if X86_64 > + select HAVE_ARCH_KASAN_VMALLOC if X86_64 > select HAVE_ARCH_KGDB > select HAVE_ARCH_MMAP_RND_BITS if MMU > select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index 6c46095cd0d9..d722230121c3 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -340,8 +340,21 @@ static noinline int vmalloc_fault(unsigned long address) > pte_t *pte; > > /* Make sure we are in vmalloc area: */ > +#ifndef CONFIG_KASAN_VMALLOC > if (!(address >= VMALLOC_START && address < VMALLOC_END)) > return -1; > +#else > + /* > + * Some of the shadow mapping for the vmalloc area lives outside the > + * pgds populated by kasan init. They are created dynamically and so > + * we may need to fault them in. > + * > + * You can observe this with test_vmalloc's align_shift_alloc_test > + */ > + if (!((address >= VMALLOC_START && address < VMALLOC_END) || > + (address >= KASAN_SHADOW_START && address < KASAN_SHADOW_END))) > + return -1; > +#endif > > /* > * Copy kernel mappings over when needed. This can also > diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c > index 296da58f3013..e2fe1c1b805c 100644 > --- a/arch/x86/mm/kasan_init_64.c > +++ b/arch/x86/mm/kasan_init_64.c > @@ -352,9 +352,19 @@ void __init kasan_init(void) > shadow_cpu_entry_end = (void *)round_up( > (unsigned long)shadow_cpu_entry_end, PAGE_SIZE); > > + /* > + * If we're in full vmalloc mode, don't back vmalloc space with early > + * shadow pages. > + */ > +#ifdef CONFIG_KASAN_VMALLOC > + kasan_populate_early_shadow( > + kasan_mem_to_shadow((void *)VMALLOC_END+1), > + shadow_cpu_entry_begin); > +#else > kasan_populate_early_shadow( > kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM), > shadow_cpu_entry_begin); > +#endif > > kasan_populate_shadow((unsigned long)shadow_cpu_entry_begin, > (unsigned long)shadow_cpu_entry_end, 0); > -- > 2.20.1 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20190725055503.19507-4-dja%40axtens.net.
