Historically kasan has not been careful about whether vmemmap_populate() internally allocates a section worth of memmap even if the parameters call for less. For example, a request to shadow map a single page results in a full section (128MB) that contains that page being mapped. Also, kasan has not been careful to handle cases where this section promotion causes overlaps / overrides of previous calls to vmemmap_populate().
Before we teach vmemmap_populate() to support sub-section hotplug, arrange for kasan to explicitly avoid vmemmap_populate_basepages(). This should be functionally equivalent to the current state since CONFIG_KASAN requires x86_64 (implies PSE) and it does not collide with sub-section hotplug support since CONFIG_KASAN disables CONFIG_MEMORY_HOTPLUG. Cc: Dmitry Vyukov <[email protected]> Cc: Alexander Potapenko <[email protected]> Cc: Andrey Ryabinin <[email protected]> Reported-by: Nicolai Stange <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- arch/x86/mm/init_64.c | 2 +- arch/x86/mm/kasan_init_64.c | 30 ++++++++++++++++++++++++++---- include/linux/mm.h | 2 ++ 3 files changed, 29 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 15173d37f399..879cd1842610 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1152,7 +1152,7 @@ static long __meminitdata addr_start, addr_end; static void __meminitdata *p_start, *p_end; static int __meminitdata node_start; -static int __meminit vmemmap_populate_hugepages(unsigned long start, +int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, int node, struct vmem_altmap *altmap) { unsigned long addr; diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index 8d63d7a104c3..e7c147140914 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -13,6 +13,25 @@ extern pgd_t early_level4_pgt[PTRS_PER_PGD]; extern struct range pfn_mapped[E820_X_MAX]; +static int __init kasan_vmemmap_populate(unsigned long start, unsigned long end) +{ + /* + * Historically kasan has not been careful about whether + * vmemmap_populate() internally allocates a section worth of memmap + * even if the parameters call for less. For example, a request to + * shadow map a single page results in a full section (128MB) that + * contains that page being mapped. Also, kasan has not been careful to + * handle cases where this section promotion causes overlaps / overrides + * of previous calls to vmemmap_populate(). Make this implicit + * dependency explicit to avoid interactions with sub-section memory + * hotplug support. + */ + if (!boot_cpu_has(X86_FEATURE_PSE)) + return -ENXIO; + + return vmemmap_populate_hugepages(start, end, NUMA_NO_NODE, NULL); +} + static int __init map_range(struct range *range) { unsigned long start; @@ -26,7 +45,7 @@ static int __init map_range(struct range *range) * to slightly speed up fastpath. In some rare cases we could cross * boundary of mapped shadow, so we just map some more here. */ - return vmemmap_populate(start, end + 1, NUMA_NO_NODE); + return kasan_vmemmap_populate(start, end + 1); } static void __init clear_pgds(unsigned long start, @@ -90,6 +109,10 @@ void __init kasan_init(void) { int i; + /* should never trigger, x86_64 implies PSE */ + WARN(!boot_cpu_has(X86_FEATURE_PSE), + "kasan requires page size extensions\n"); + #ifdef CONFIG_KASAN_INLINE register_die_notifier(&kasan_die_notifier); #endif @@ -114,9 +137,8 @@ void __init kasan_init(void) kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM), kasan_mem_to_shadow((void *)__START_KERNEL_map)); - vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext), - (unsigned long)kasan_mem_to_shadow(_end), - NUMA_NO_NODE); + kasan_vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext), + (unsigned long)kasan_mem_to_shadow(_end)); kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), (void *)KASAN_SHADOW_END); diff --git a/include/linux/mm.h b/include/linux/mm.h index 5f01c88f0800..601560ad3981 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2423,6 +2423,8 @@ void vmemmap_verify(pte_t *, int, unsigned long, unsigned long); int vmemmap_populate_basepages(unsigned long start, unsigned long end, int node); int vmemmap_populate(unsigned long start, unsigned long end, int node); +int vmemmap_populate_hugepages(unsigned long start, unsigned long end, int node, + struct vmem_altmap *altmap); void vmemmap_populate_print_last(void); #ifdef CONFIG_MEMORY_HOTPLUG void vmemmap_free(unsigned long start, unsigned long end);
