Re: [PATCH v3 07/28] hw/9pfs: Replace g_memdup() by g_memdup2()

[Christian Schoenebeck]

On Freitag, 3. September 2021 19:44:49 CEST Philippe Mathieu-Daudé wrote:
> Per
> https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-n
> ow/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>
> ---
>  hw/9pfs/9p-synth.c | 2 +-
>  hw/9pfs/9p.c       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
> index b38088e0664..d6168c653d2 100644
> --- a/hw/9pfs/9p-synth.c
> +++ b/hw/9pfs/9p-synth.c
> @@ -497,7 +497,7 @@ static int synth_name_to_path(FsContext *ctx, V9fsPath
> *dir_path, out:
>      /* Copy the node pointer to fid */
>      g_free(target->data);
> -    target->data = g_memdup(&node, sizeof(void *));
> +    target->data = g_memdup2(&node, sizeof(void *));
>      target->size = sizeof(void *);
>      return 0;
>  }

That's Ok, trivial change.

> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index c857b313213..a80166fcaff 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -202,7 +202,7 @@ void v9fs_path_copy(V9fsPath *dst, const V9fsPath *src)
>  {
>      v9fs_path_free(dst);
>      dst->size = src->size;
> -    dst->data = g_memdup(src->data, src->size);
> +    dst->data = g_memdup2(src->data, src->size);
>  }
> 
>  int v9fs_name_to_path(V9fsState *s, V9fsPath *dirpath,

src->size is actually just 16 bit (fsdev/file-op-9p.h):

struct V9fsPath {
    uint16_t size;
    char *data;
};

Should (still) be Ok as well as V9fsPath is about file system pathes which are 
currently limited to 4k (PATH_MAX).

Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>

Best regards,
Christian Schoenebeck