linux-kernel - [PATCH v2] lib: test_overflow: Avoid tainting the kernel and fix wrap size

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Message-ID: <201905282012.0A8767E24@keescook>
Date:   Tue, 28 May 2019 20:14:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] lib: test_overflow: Avoid tainting the kernel and fix
 wrap size

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 <rdunlap@...radead.org>
Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Fixes: ca90800a91ba ("test_overflow: Add memory allocation overflow tests")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
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)				\
-- 
2.17.1


-- 
Kees Cook