Re: [Qemu-devel] [PATCH] throttle: Assert that bkt->max is valid in throttle_compute_wait()

[Eric Blake <eblake@redhat.com>]

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On 09/13/2017 03:28 AM, Alberto Garcia wrote:
> If bkt->max == 0 and bkt->burst_length > 1 then we could have a
> division by 0 in throttle_do_compute_wait(). That configuration is
> however not permitted and is already detected by throttle_is_valid(),
> but let's assert it in throttle_compute_wait() to make it explicit.
> 
> Found by Coverity (CID: 1381016).
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  util/throttle.c | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/util/throttle.c b/util/throttle.c
> index 06bf916adc..b38e742da5 100644
> --- a/util/throttle.c
> +++ b/util/throttle.c
> @@ -124,6 +124,7 @@ int64_t throttle_compute_wait(LeakyBucket *bkt)
>      /* If the main bucket is not full yet we still have to check the
>       * burst bucket in order to enforce the burst limit */
>      if (bkt->burst_length > 1) {
> +        assert(bkt->max > 0); /* see throttle_is_valid() */
>          extra = bkt->burst_level - burst_bucket_size;
>          if (extra > 0) {
>              return throttle_do_compute_wait(bkt->max, extra);
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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