Re: [PATCH 1/2] migration: Assert that migrate_multifd_compression() returns an in-range value

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> Coverity complains that when we use the return value from
> migrate_multifd_compression() as an array index:
>   multifd_recv_state->ops = multifd_ops[migrate_multifd_compression()];
> 
> that this might overrun the array (which is declared to have size
> MULTIFD_COMPRESSION__MAX).  This is because the function return type
> is MultiFDCompression, which is an autogenerated enum.  The code
> generator includes the "one greater than the maximum possible value"
> MULTIFD_COMPRESSION__MAX in the enum, even though this is not
> actually a valid value for the enum, and this makes Coverity think
> that migrate_multifd_compression() could return that __MAX value and
> index off the end of the array.
> 
> Suppress the Coverity error by asserting that the value we're going
> to return is within range.
> 
> Resolves: Coverity CID 1487239, 1487254
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/migration.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index e03f698a3ca..befd4c58a69 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2617,6 +2617,7 @@ MultiFDCompression migrate_multifd_compression(void)
>  
>      s = migrate_get_current();
>  
> +    assert(s->parameters.multifd_compression < MULTIFD_COMPRESSION__MAX);
>      return s->parameters.multifd_compression;
>  }
>  
> -- 
> 2.25.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK