Re: [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds

[Markus Armbruster]

Anthony Liguori <address@hidden> writes:

> qemu_malloc() does not allow size=0 to be passed in and aborts on this 
> behavior.
>
> Unfortunately, there is good reason to believe that within qemu, there are a
> number of, so far, undetected places that assume size=0 can be safely passed.
> Since we do not want to abort unnecessarily in production builds, return
> qemu_malloc(1) whenever the version file indicates that this is a production
> build.
>
> Also introduce --enable-zero-malloc/--disable-zero-malloc to make this 
> behavior
> overridable.
>
> Signed-off-by: Anthony Liguori <address@hidden>
> ---
>  configure     |   24 +++++++++++++++++++++++-
>  qemu-malloc.c |   17 +++++++++++++----
>  2 files changed, 36 insertions(+), 5 deletions(-)
>
[...]
> diff --git a/qemu-malloc.c b/qemu-malloc.c
> index 295d185..e82af26 100644
> --- a/qemu-malloc.c
> +++ b/qemu-malloc.c
> @@ -42,21 +42,30 @@ void qemu_free(void *ptr)
>      free(ptr);
>  }
>  
> +static int allow_zero_malloc(void)
> +{
> +#if defined(CONFIG_ZERO_MALLOC)
> +    return 1;
> +#else
> +    return 0;
> +#endif
> +}
> +
>  void *qemu_malloc(size_t size)
>  {
> -    if (!size) {
> +    if (!size && !allow_zero_malloc()) {
>          abort();
>      }
> -    return oom_check(malloc(size));
> +    return oom_check(malloc(size ? size : 1));
>  }
>  
>  void *qemu_realloc(void *ptr, size_t size)
>  {
>      if (size) {
>          return oom_check(realloc(ptr, size));
> -    } else {
> +    } else if (allow_zero_malloc()) {
>          if (ptr) {
> -            return realloc(ptr, size);
> +            return realloc(ptr, size ? size : 1);
>          }
>      }
>      abort();

This still aborts on qemu_realloc(NULL, 0), even with
CONFIG_ZERO_MALLOC.  Intentional?