[PATCH] test_bitmap: Do not accidentally use stack VLA

[Kees Cook]

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 
Cc: Andy Shevchenko 
Cc: Matthew Wilcox 
Signed-off-by: Kees Cook 
---
 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

[PATCH] test_bitmap: Do not accidentally use stack VLA

[Kees Cook]

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 
Cc: Andy Shevchenko 
Cc: Matthew Wilcox 
Signed-off-by: Kees Cook 
---
 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