Re: [PATCH v3 05/28] block/qcow2-bitmap: Replace g_memdup() by g_memdup2()

[Eric Blake]

On Fri, Sep 03, 2021 at 07:44:47PM +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>
> ---
>  block/qcow2-bitmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index 8fb47315515..218a0dc712a 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -1599,7 +1599,7 @@ bool 
> qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs,
>                             name);
>                  goto fail;
>              }
> -            tb = g_memdup(&bm->table, sizeof(bm->table));
> +            tb = g_memdup2(&bm->table, sizeof(bm->table));

Trivially safe.  It might be worth a comment in the various commit
messages for which patches are trivially safe (because the argument
was directly from sizeof), and which would require a larger audit of
callers to see if we had any (unlikely) bug (such as patch 3/28).

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

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