Re: [Qemu-devel] [PATCH] bitmap: assert that start and nr are non negative

[Fam Zheng <famz@redhat.com>]

On Thu, 01/19 17:43, Peter Lieven wrote:
> commit e1123a3b introduced a data corruption regression
> in the iscsi driver because it passed -1 as nr to bitmap_set
> and bitmap_clear. Add an assertion to catch such flaws earlier.
> 
> Suggested-by: Fam Zheng <famz@redhat.com>
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  util/bitmap.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/util/bitmap.c b/util/bitmap.c
> index 43ed011..c1a84ca 100644
> --- a/util/bitmap.c
> +++ b/util/bitmap.c
> @@ -164,6 +164,8 @@ void bitmap_set(unsigned long *map, long start, long nr)
>      int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
>      unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
>  
> +    assert(start >= 0 && nr >= 0);
> +
>      while (nr - bits_to_set >= 0) {
>          *p |= mask_to_set;
>          nr -= bits_to_set;
> @@ -184,6 +186,8 @@ void bitmap_set_atomic(unsigned long *map, long start, long nr)
>      int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
>      unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
>  
> +    assert(start >= 0 && nr >= 0);
> +
>      /* First word */
>      if (nr - bits_to_set > 0) {
>          atomic_or(p, mask_to_set);
> @@ -221,6 +225,8 @@ void bitmap_clear(unsigned long *map, long start, long nr)
>      int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
>      unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
>  
> +    assert(start >= 0 && nr >= 0);
> +
>      while (nr - bits_to_clear >= 0) {
>          *p &= ~mask_to_clear;
>          nr -= bits_to_clear;
> @@ -243,6 +249,8 @@ bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr)
>      unsigned long dirty = 0;
>      unsigned long old_bits;
>  
> +    assert(start >= 0 && nr >= 0);
> +
>      /* First word */
>      if (nr - bits_to_clear > 0) {
>          old_bits = atomic_fetch_and(p, ~mask_to_clear);
> -- 
> 1.9.1
> 
> 

Reviewed-by: Fam Zheng <famz@redhat.com>