kasan: improve vmalloc tests

Update the existing vmalloc_oob() test to account for the specifics of the
tag-based modes.  Also add a few new checks and comments.

Add new vmalloc-related tests:

 - vmalloc_helpers_tags() to check that exported vmalloc helpers can
   handle tagged pointers.

 - vmap_tags() to check that SW_TAGS mode properly tags vmap() mappings.

 - vm_map_ram_tags() to check that SW_TAGS mode properly tags
   vm_map_ram() mappings.

 - vmalloc_percpu() to check that SW_TAGS mode tags regions allocated
   for __alloc_percpu(). The tagging of per-cpu mappings is best-effort;
   proper tagging is tracked in [1].

[1] https://bugzilla.kernel.org/show_bug.cgi?id=215019

[sfr@canb.auug.org.au: similar to "kasan: test: fix compatibility with FORTIFY_SOURCE"]
Link: https://lkml.kernel.org/r/20220128144801.73f5ced0@canb.auug.org.au
Link: https://lkml.kernel.org/r/865c91ba49b90623ab50c7526b79ccb955f544f0.1644950160.git.andreyknvl@google.com
[andreyknvl@google.com: set_memory_rw/ro() are not exported to modules]
Link: https://lkml.kernel.org/r/019ac41602e0c4a7dfe96dc8158a95097c2b2ebd.1645554036.git.andreyknvl@google.com
[akpm@linux-foundation.org: fix build]

Cc: Andrey Konovalov <andreyknvl@gmail.com>
[andreyknvl@google.com: vmap_tags() and vm_map_ram_tags() pass invalid page array size]
Link: https://lkml.kernel.org/r/bbdc1c0501c5275e7f26fdb8e2a7b14a40a9f36b.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 3b413f8c8a7154816fa763c37f7846021504a645..2addd0c66acfcc9ef70a47119375ac4e0f86057e 100644 (file)
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/vmalloc.h>
+#include <linux/set_memory.h>
 
 #include <asm/page.h>
 
@@ -1057,21 +1058,186 @@ static void kmalloc_double_kzfree(struct kunit *test)
        KUNIT_EXPECT_KASAN_FAIL(test, kfree_sensitive(ptr));
 }
 
+static void vmalloc_helpers_tags(struct kunit *test)
+{
+       void *ptr;
+
+       /* This test is intended for tag-based modes. */
+       KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
+
+       KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_VMALLOC);
+
+       ptr = vmalloc(PAGE_SIZE);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+
+       /* Check that the returned pointer is tagged. */
+       KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
+       KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
+
+       /* Make sure exported vmalloc helpers handle tagged pointers. */
+       KUNIT_ASSERT_TRUE(test, is_vmalloc_addr(ptr));
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, vmalloc_to_page(ptr));
+
+#if !IS_MODULE(CONFIG_KASAN_KUNIT_TEST)
+       {
+               int rv;
+
+               /* Make sure vmalloc'ed memory permissions can be changed. */
+               rv = set_memory_ro((unsigned long)ptr, 1);
+               KUNIT_ASSERT_GE(test, rv, 0);
+               rv = set_memory_rw((unsigned long)ptr, 1);
+               KUNIT_ASSERT_GE(test, rv, 0);
+       }
+#endif
+
+       vfree(ptr);
+}
+
 static void vmalloc_oob(struct kunit *test)
 {
-       void *area;
+       char *v_ptr, *p_ptr;
+       struct page *page;
+       size_t size = PAGE_SIZE / 2 - KASAN_GRANULE_SIZE - 5;
 
        KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_VMALLOC);
 
+       v_ptr = vmalloc(size);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, v_ptr);
+
+       OPTIMIZER_HIDE_VAR(v_ptr);
+
        /*
-        * We have to be careful not to hit the guard page.
+        * We have to be careful not to hit the guard page in vmalloc tests.
         * The MMU will catch that and crash us.
         */
-       area = vmalloc(3000);
-       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, area);
 
-       KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)area)[3100]);
-       vfree(area);
+       /* Make sure in-bounds accesses are valid. */
+       v_ptr[0] = 0;
+       v_ptr[size - 1] = 0;
+
+       /*
+        * An unaligned access past the requested vmalloc size.
+        * Only generic KASAN can precisely detect these.
+        */
+       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+               KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)v_ptr)[size]);
+
+       /* An aligned access into the first out-of-bounds granule. */
+       KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)v_ptr)[size + 5]);
+
+       /* Check that in-bounds accesses to the physical page are valid. */
+       page = vmalloc_to_page(v_ptr);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, page);
+       p_ptr = page_address(page);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p_ptr);
+       p_ptr[0] = 0;
+
+       vfree(v_ptr);
+
+       /*
+        * We can't check for use-after-unmap bugs in this nor in the following
+        * vmalloc tests, as the page might be fully unmapped and accessing it
+        * will crash the kernel.
+        */
+}
+
+static void vmap_tags(struct kunit *test)
+{
+       char *p_ptr, *v_ptr;
+       struct page *p_page, *v_page;
+
+       /*
+        * This test is specifically crafted for the software tag-based mode,
+        * the only tag-based mode that poisons vmap mappings.
+        */
+       KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_SW_TAGS);
+
+       KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_VMALLOC);
+
+       p_page = alloc_pages(GFP_KERNEL, 1);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p_page);
+       p_ptr = page_address(p_page);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p_ptr);
+
+       v_ptr = vmap(&p_page, 1, VM_MAP, PAGE_KERNEL);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, v_ptr);
+
+       /*
+        * We can't check for out-of-bounds bugs in this nor in the following
+        * vmalloc tests, as allocations have page granularity and accessing
+        * the guard page will crash the kernel.
+        */
+
+       KUNIT_EXPECT_GE(test, (u8)get_tag(v_ptr), (u8)KASAN_TAG_MIN);
+       KUNIT_EXPECT_LT(test, (u8)get_tag(v_ptr), (u8)KASAN_TAG_KERNEL);
+
+       /* Make sure that in-bounds accesses through both pointers work. */
+       *p_ptr = 0;
+       *v_ptr = 0;
+
+       /* Make sure vmalloc_to_page() correctly recovers the page pointer. */
+       v_page = vmalloc_to_page(v_ptr);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, v_page);
+       KUNIT_EXPECT_PTR_EQ(test, p_page, v_page);
+
+       vunmap(v_ptr);
+       free_pages((unsigned long)p_ptr, 1);
+}
+
+static void vm_map_ram_tags(struct kunit *test)
+{
+       char *p_ptr, *v_ptr;
+       struct page *page;
+
+       /*
+        * This test is specifically crafted for the software tag-based mode,
+        * the only tag-based mode that poisons vm_map_ram mappings.
+        */
+       KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_SW_TAGS);
+
+       page = alloc_pages(GFP_KERNEL, 1);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, page);
+       p_ptr = page_address(page);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p_ptr);
+
+       v_ptr = vm_map_ram(&page, 1, -1);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, v_ptr);
+
+       KUNIT_EXPECT_GE(test, (u8)get_tag(v_ptr), (u8)KASAN_TAG_MIN);
+       KUNIT_EXPECT_LT(test, (u8)get_tag(v_ptr), (u8)KASAN_TAG_KERNEL);
+
+       /* Make sure that in-bounds accesses through both pointers work. */
+       *p_ptr = 0;
+       *v_ptr = 0;
+
+       vm_unmap_ram(v_ptr, 1);
+       free_pages((unsigned long)p_ptr, 1);
+}
+
+static void vmalloc_percpu(struct kunit *test)
+{
+       char __percpu *ptr;
+       int cpu;
+
+       /*
+        * This test is specifically crafted for the software tag-based mode,
+        * the only tag-based mode that poisons percpu mappings.
+        */
+       KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_SW_TAGS);
+
+       ptr = __alloc_percpu(PAGE_SIZE, PAGE_SIZE);
+
+       for_each_possible_cpu(cpu) {
+               char *c_ptr = per_cpu_ptr(ptr, cpu);
+
+               KUNIT_EXPECT_GE(test, (u8)get_tag(c_ptr), (u8)KASAN_TAG_MIN);
+               KUNIT_EXPECT_LT(test, (u8)get_tag(c_ptr), (u8)KASAN_TAG_KERNEL);
+
+               /* Make sure that in-bounds accesses don't crash the kernel. */
+               *c_ptr = 0;
+       }
+
+       free_percpu(ptr);
 }
 
 /*
@@ -1105,6 +1271,18 @@ static void match_all_not_assigned(struct kunit *test)
                KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
                free_pages((unsigned long)ptr, order);
        }
+
+       if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
+               return;
+
+       for (i = 0; i < 256; i++) {
+               size = (get_random_int() % 1024) + 1;
+               ptr = vmalloc(size);
+               KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+               KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
+               KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
+               vfree(ptr);
+       }
 }
 
 /* Check that 0xff works as a match-all pointer tag for tag-based modes. */
@@ -1210,7 +1388,11 @@ static struct kunit_case kasan_kunit_test_cases[] = {
        KUNIT_CASE(kasan_bitops_generic),
        KUNIT_CASE(kasan_bitops_tags),
        KUNIT_CASE(kmalloc_double_kzfree),
+       KUNIT_CASE(vmalloc_helpers_tags),
        KUNIT_CASE(vmalloc_oob),
+       KUNIT_CASE(vmap_tags),
+       KUNIT_CASE(vm_map_ram_tags),
+       KUNIT_CASE(vmalloc_percpu),
        KUNIT_CASE(match_all_not_assigned),
        KUNIT_CASE(match_all_ptr_tag),
        KUNIT_CASE(match_all_mem_tag),