From f260fd59e3f387432bda51072fff4494fba10b91 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 17 May 2022 14:44:20 -0700 Subject: [PATCH] lkdtm/heap: Hide allocation size from -Warray-bounds With the kmalloc() size annotations, GCC is smart enough to realize that LKDTM is intentionally writing past the end of the buffer. This is on purpose, of course, so hide the buffer from the optimizer. Silences: ../drivers/misc/lkdtm/heap.c: In function 'lkdtm_SLAB_LINEAR_OVERFLOW': ../drivers/misc/lkdtm/heap.c:59:13: warning: array subscript 256 is outside array bounds of 'void[1020]' [-Warray-bounds] 59 | data[1024 / sizeof(u32)] = 0x12345678; | ~~~~^~~~~~~~~~~~~~~~~~~~ In file included from ../drivers/misc/lkdtm/heap.c:7: In function 'kmalloc', inlined from 'lkdtm_SLAB_LINEAR_OVERFLOW' at ../drivers/misc/lkdtm/heap.c:54:14: ../include/linux/slab.h:581:24: note: at offset 1024 into object of size 1020 allocated by 'kmem_cache_alloc_trace' 581 | return kmem_cache_alloc_trace( | ^~~~~~~~~~~~~~~~~~~~~~~ 582 | kmalloc_caches[kmalloc_type(flags)][index], | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 583 | flags, size); | ~~~~~~~~~~~~ Cc: Greg Kroah-Hartman Cc: Arnd Bergmann Signed-off-by: Kees Cook --- drivers/misc/lkdtm/heap.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c index 5d3b92c..6251607 100644 --- a/drivers/misc/lkdtm/heap.c +++ b/drivers/misc/lkdtm/heap.c @@ -56,6 +56,7 @@ static void lkdtm_SLAB_LINEAR_OVERFLOW(void) return; pr_info("Attempting slab linear overflow ...\n"); + OPTIMIZER_HIDE_VAR(data); data[1024 / sizeof(u32)] = 0x12345678; kfree(data); } -- 2.7.4