Once __alloc_size hints have been added, the compiler will (correctly!)
see this as an overflow. We are, however, trying to test for this
condition at run-time (not compile-time), so work around it with a
volatile int offset.
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
drivers/misc/lkdtm/heap.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 3d9aae5821a0..8a92f5a800fa 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -12,6 +12,13 @@ static struct kmem_cache *double_free_cache;
static struct kmem_cache *a_cache;
static struct kmem_cache *b_cache;
+/*
+ * Using volatile here means the compiler cannot ever make assumptions
+ * about this value. This means compile-time length checks involving
+ * this variable cannot be performed; only run-time checks.
+ */
+static volatile int __offset = 1;
+
/*
* If there aren't guard pages, it's likely that a consecutive allocation will
* let us overflow into the second allocation without overwriting something real.
@@ -24,7 +31,7 @@ void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
two = vzalloc(PAGE_SIZE);
pr_info("Attempting vmalloc linear overflow ...\n");
- memset(one, 0xAA, PAGE_SIZE + 1);
+ memset(one, 0xAA, PAGE_SIZE + __offset);
vfree(two);
vfree(one);
--
2.30.2
