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Subject[PATCH] test_bitmap: Do not accidentally use stack VLA
This avoids an accidental stack VLA (since the compiler thinks the value
of "len" can change, even when marked "const"). This just replaces it
with a #define so it will DTRT.

Seen with -Wvla. Fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621

Cc: Yury Norov <ynorov@caviumnetworks.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
lib/test_bitmap.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index b3f235baa05d..756f20ad03db 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -292,15 +292,17 @@ static void __init test_bitmap_parselist(void)
}
}

+#define EXP_BYTES (sizeof(exp) * 8)
+
static void __init test_bitmap_arr32(void)
{
- unsigned int nbits, next_bit, len = sizeof(exp) * 8;
+ unsigned int nbits, next_bit;
u32 arr[sizeof(exp) / 4];
- DECLARE_BITMAP(bmap2, len);
+ DECLARE_BITMAP(bmap2, EXP_BYTES);

memset(arr, 0xa5, sizeof(arr));

- for (nbits = 0; nbits < len; ++nbits) {
+ for (nbits = 0; nbits < EXP_BYTES; ++nbits) {
bitmap_to_arr32(arr, exp, nbits);
bitmap_from_arr32(bmap2, arr, nbits);
expect_eq_bitmap(bmap2, exp, nbits);
@@ -312,7 +314,7 @@ static void __init test_bitmap_arr32(void)
" tail is not safely cleared: %d\n",
nbits, next_bit);

- if (nbits < len - 32)
+ if (nbits < EXP_BYTES - 32)
expect_eq_uint(arr[DIV_ROUND_UP(nbits, 32)],
0xa5a5a5a5);
}
--
2.7.4

--
Kees Cook
Pixel Security

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