kasan: detect invalid frees for large objects

Patch series "kasan: detect invalid frees".

KASAN detects double-frees, but does not detect invalid-frees (when a
pointer into a middle of heap object is passed to free).  We recently had
a very unpleasant case in crypto code which freed an inner object inside
of a heap allocation.  This left unnoticed during free, but totally
corrupted heap and later lead to a bunch of random crashes all over kernel
code.

Detect invalid frees.

This patch (of 5):

Detect frees of pointers into middle of large heap objects.

I dropped const from kasan_kfree_large() because it starts propagating
through a bunch of functions in kasan_report.c, slab/slub nearest_obj(),
all of their local variables, fixup_red_left(), etc.

Link: http://lkml.kernel.org/r/1b45b4fe1d20fc0de1329aab674c1dd973fee723.1514378558.git.dvyukov@google.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>a
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 2724f86c4cef7..e9c5d765be66c 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -94,6 +94,37 @@ static noinline void __init kmalloc_pagealloc_oob_right(void)
 	ptr[size] = 0;
 	kfree(ptr);
 }
+
+static noinline void __init kmalloc_pagealloc_uaf(void)
+{
+	char *ptr;
+	size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
+
+	pr_info("kmalloc pagealloc allocation: use-after-free\n");
+	ptr = kmalloc(size, GFP_KERNEL);
+	if (!ptr) {
+		pr_err("Allocation failed\n");
+		return;
+	}
+
+	kfree(ptr);
+	ptr[0] = 0;
+}
+
+static noinline void __init kmalloc_pagealloc_invalid_free(void)
+{
+	char *ptr;
+	size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
+
+	pr_info("kmalloc pagealloc allocation: invalid-free\n");
+	ptr = kmalloc(size, GFP_KERNEL);
+	if (!ptr) {
+		pr_err("Allocation failed\n");
+		return;
+	}
+
+	kfree(ptr + 1);
+}
 #endif
 
 static noinline void __init kmalloc_large_oob_right(void)
@@ -505,6 +536,8 @@ static int __init kmalloc_tests_init(void)
 	kmalloc_node_oob_right();
 #ifdef CONFIG_SLUB
 	kmalloc_pagealloc_oob_right();
+	kmalloc_pagealloc_uaf();
+	kmalloc_pagealloc_invalid_free();
 #endif
 	kmalloc_large_oob_right();
 	kmalloc_oob_krealloc_more();