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* [PATCH] lkdtm/heap: Avoid __alloc_size hint warning
@ 2021-08-18  4:45 Kees Cook
  2021-08-18 14:01 ` Greg Kroah-Hartman
  0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2021-08-18  4:45 UTC (permalink / raw)
  To: Greg Kroah-Hartman; +Cc: Kees Cook, linux-kernel, linux-hardening

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, so work around it with a volatile int.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm/heap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 3d9aae5821a0..e59fcbe00ae0 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -12,6 +12,8 @@ static struct kmem_cache *double_free_cache;
 static struct kmem_cache *a_cache;
 static struct kmem_cache *b_cache;
 
+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 +26,7 @@ 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


^ permalink raw reply	[flat|nested] 3+ messages in thread

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2021-08-18  4:45 [PATCH] lkdtm/heap: Avoid __alloc_size hint warning Kees Cook
2021-08-18 14:01 ` Greg Kroah-Hartman
2021-08-18 17:32   ` Kees Cook

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