On Thu, May 6, 2021 at 4:58 PM Andrey Konovalov andreyknvl@gmail.com wrote:
On Fri, May 7, 2021 at 1:47 AM Peter Collingbourne pcc@google.com wrote:
On Thu, May 6, 2021 at 3:12 PM Andrey Konovalov andreyknvl@gmail.com wrote:
On Thu, May 6, 2021 at 11:20 PM Peter Collingbourne pcc@google.com wrote:
These tests deliberately access these arrays out of bounds, which will cause the dynamic local bounds checks inserted by CONFIG_UBSAN_LOCAL_BOUNDS to fail and panic the kernel. To avoid this problem, access the arrays via volatile pointers, which will prevent the compiler from being able to determine the array bounds.
Signed-off-by: Peter Collingbourne pcc@google.com Cc: stable@vger.kernel.org Link: https://linux-review.googlesource.com/id/I90b1713fbfa1bf68ff895aef099ea77b98...
lib/test_kasan.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c index dc05cfc2d12f..2a078e8e7b8e 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -654,8 +654,8 @@ static char global_array[10];
static void kasan_global_oob(struct kunit *test) {
volatile int i = 3;char *p = &global_array[ARRAY_SIZE(global_array) + i];
char *volatile array = global_array;char *p = &array[ARRAY_SIZE(global_array) + 3];Nit: in the kernel, "volatile" usually comes before the pointer type.
That would refer to a different type. "volatile char *" is a pointer to volatile char, while "char *volatile" is a volatile pointer to char. The latter is what we want here, because we want to prevent the compiler from inferring things about the pointer itself (i.e. its array bounds), not the data that it refers to.
I see. This is unusual. I'd say this needs to be explicitly explained in the commit message, as well as in a comment in the code.
Done in v2.
Peter