x86/kasan: support KASAN_VMALLOC

In the case where KASAN directly allocates memory to back vmalloc space,
don't map the early shadow page over it.

We prepopulate pgds/p4ds for the range that would otherwise be empty.
This is required to get it synced to hardware on boot, allowing the
lower levels of the page tables to be filled dynamically.

Link: http://lkml.kernel.org/r/20191031093909.9228-5-dja@axtens.net
Signed-off-by: Daniel Axtens <dja@axtens.net>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0cb1756..5e89499 100644 (file)
--- 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/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 296da58..cf5bc37 100644 (file)
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -245,6 +245,49 @@ static void __init kasan_map_early_shadow(pgd_t *pgd)
        } while (pgd++, addr = next, addr != end);
 }
 
+static void __init kasan_shallow_populate_p4ds(pgd_t *pgd,
+                                              unsigned long addr,
+                                              unsigned long end)
+{
+       p4d_t *p4d;
+       unsigned long next;
+       void *p;
+
+       p4d = p4d_offset(pgd, addr);
+       do {
+               next = p4d_addr_end(addr, end);
+
+               if (p4d_none(*p4d)) {
+                       p = early_alloc(PAGE_SIZE, NUMA_NO_NODE, true);
+                       p4d_populate(&init_mm, p4d, p);
+               }
+       } while (p4d++, addr = next, addr != end);
+}
+
+static void __init kasan_shallow_populate_pgds(void *start, void *end)
+{
+       unsigned long addr, next;
+       pgd_t *pgd;
+       void *p;
+
+       addr = (unsigned long)start;
+       pgd = pgd_offset_k(addr);
+       do {
+               next = pgd_addr_end(addr, (unsigned long)end);
+
+               if (pgd_none(*pgd)) {
+                       p = early_alloc(PAGE_SIZE, NUMA_NO_NODE, true);
+                       pgd_populate(&init_mm, pgd, p);
+               }
+
+               /*
+                * we need to populate p4ds to be synced when running in
+                * four level mode - see sync_global_pgds_l4()
+                */
+               kasan_shallow_populate_p4ds(pgd, addr, next);
+       } while (pgd++, addr = next, addr != (unsigned long)end);
+}
+
 #ifdef CONFIG_KASAN_INLINE
 static int kasan_die_handler(struct notifier_block *self,
                             unsigned long val,
@@ -354,6 +397,24 @@ void __init kasan_init(void)
 
        kasan_populate_early_shadow(
                kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
+               kasan_mem_to_shadow((void *)VMALLOC_START));
+
+       /*
+        * If we're in full vmalloc mode, don't back vmalloc space with early
+        * shadow pages. Instead, prepopulate pgds/p4ds so they are synced to
+        * the global table and we can populate the lower levels on demand.
+        */
+       if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
+               kasan_shallow_populate_pgds(
+                       kasan_mem_to_shadow((void *)VMALLOC_START),
+                       kasan_mem_to_shadow((void *)VMALLOC_END));
+       else
+               kasan_populate_early_shadow(
+                       kasan_mem_to_shadow((void *)VMALLOC_START),
+                       kasan_mem_to_shadow((void *)VMALLOC_END));
+
+       kasan_populate_early_shadow(
+               kasan_mem_to_shadow((void *)VMALLOC_END + 1),
                shadow_cpu_entry_begin);
 
        kasan_populate_shadow((unsigned long)shadow_cpu_entry_begin,