Re: [PATCH v3 03/28] qapi: Replace g_memdup() by g_memdup2()

[Eric Blake <eblake@redhat.com>]

On Fri, Sep 03, 2021 at 07:44:45PM +0200, Philippe Mathieu-Daudé wrote:
> Per https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538
> 
>   The old API took the size of the memory to duplicate as a guint,
>   whereas most memory functions take memory sizes as a gsize. This
>   made it easy to accidentally pass a gsize to g_memdup(). For large
>   values, that would lead to a silent truncation of the size from 64
>   to 32 bits, and result in a heap area being returned which is
>   significantly smaller than what the caller expects. This can likely
>   be exploited in various modules to cause a heap buffer overflow.
> 
> Replace g_memdup() by the safer g_memdup2() wrapper.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  qapi/qapi-clone-visitor.c | 16 ++++++++--------
>  qapi/qapi-visit-core.c    |  6 ++++--
>  2 files changed, 12 insertions(+), 10 deletions(-)

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

> 
> diff --git a/qapi/qapi-clone-visitor.c b/qapi/qapi-clone-visitor.c
> index c45c5caa3b8..b014119d368 100644
> --- a/qapi/qapi-clone-visitor.c
> +++ b/qapi/qapi-clone-visitor.c
> @@ -37,7 +37,7 @@ static bool qapi_clone_start_struct(Visitor *v, const char *name, void **obj,
>          return true;
>      }
>  
> -    *obj = g_memdup(*obj, size);
> +    *obj = g_memdup2(*obj, size);

I did not audit whether any callers were previously vulnerable,
although I suspect most (if not all) callers were from the generated
QAPI code passing in the results of sizeof, and none of our QAPI types
are 4G large to cause overflow.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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