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* [PATCH v2] lib: test_overflow: Avoid tainting the kernel and fix wrap size
@ 2019-05-29  3:14 Kees Cook
  0 siblings, 0 replies; only message in thread
From: Kees Cook @ 2019-05-29  3:14 UTC (permalink / raw)
  To: Andrew Morton; +Cc: Randy Dunlap, Rasmus Villemoes, Joe Perches, linux-kernel

This adds __GFP_NOWARN to the kmalloc()-portions of the overflow test to
avoid tainting the kernel. Additionally fixes up the math on wrap size
to be architecture and page size agnostic.

Reported-by: Randy Dunlap <>
Suggested-by: Rasmus Villemoes <>
Fixes: ca90800a91ba ("test_overflow: Add memory allocation overflow tests")
Signed-off-by: Kees Cook <>
v2: fix leftover __GFP_NOWARN (joe)
 lib/test_overflow.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/test_overflow.c b/lib/test_overflow.c
index fc680562d8b6..7a4b6f6c5473 100644
--- a/lib/test_overflow.c
+++ b/lib/test_overflow.c
@@ -486,16 +486,17 @@ static int __init test_overflow_shift(void)
  * Deal with the various forms of allocator arguments. See comments above
  * the DEFINE_TEST_ALLOC() instances for mapping of the "bits".
-#define alloc010(alloc, arg, sz) alloc(sz, GFP_KERNEL)
-#define alloc011(alloc, arg, sz) alloc(sz, GFP_KERNEL, NUMA_NO_NODE)
+#define alloc_GFP		 (GFP_KERNEL | __GFP_NOWARN)
+#define alloc010(alloc, arg, sz) alloc(sz, alloc_GFP)
+#define alloc011(alloc, arg, sz) alloc(sz, alloc_GFP, NUMA_NO_NODE)
 #define alloc000(alloc, arg, sz) alloc(sz)
 #define alloc001(alloc, arg, sz) alloc(sz, NUMA_NO_NODE)
-#define alloc110(alloc, arg, sz) alloc(arg, sz, GFP_KERNEL)
+#define alloc110(alloc, arg, sz) alloc(arg, sz, alloc_GFP)
 #define free0(free, arg, ptr)	 free(ptr)
 #define free1(free, arg, ptr)	 free(arg, ptr)
-/* Wrap around to 8K */
-#define TEST_SIZE		(9 << PAGE_SHIFT)
+/* Wrap around to 16K */
+#define TEST_SIZE		(5 * 4096)
 #define DEFINE_TEST_ALLOC(func, free_func, want_arg, want_gfp, want_node)\
 static int __init test_ ## func (void *arg)				\

Kees Cook

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2019-05-29  3:14 [PATCH v2] lib: test_overflow: Avoid tainting the kernel and fix wrap size Kees Cook

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