Re: [Qemu-devel] [PATCH for-3.1 v3 1/2] usb-mtp: fix utf16_to_str

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/12/18 11:10, Gerd Hoffmann wrote:
> Make utf16_to_str return an allocated string.  Remove the assumtion that
> the number of string bytes equals the number of utf16 chars (which is
> only true for ascii chars).  Instead call wcstombs twice, once to figure
> the storage size and once for the actual conversion (as suggested by the
> wcstombs manpage).
> 
> Reported-by: Michael Hanselmann <public@hansmi.ch>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  hw/usb/dev-mtp.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
> index 00a3691bae..0f6a9702ef 100644
> --- a/hw/usb/dev-mtp.c
> +++ b/hw/usb/dev-mtp.c
> @@ -1593,17 +1593,23 @@ static void usb_mtp_cancel_packet(USBDevice *dev, USBPacket *p)
>      fprintf(stderr, "%s\n", __func__);
>  }
>  
> -static void utf16_to_str(uint8_t len, uint16_t *arr, char *name)
> +static char *utf16_to_str(uint8_t len, uint16_t *arr)
>  {
> -    int count;
> -    wchar_t *wstr = g_new0(wchar_t, len);
> +    wchar_t *wstr = g_new0(wchar_t, len + 1);
> +    int count, dlen;
> +    char *dest;
>  
>      for (count = 0; count < len; count++) {
> +        /* FIXME: not working for surrogate pairs */
>          wstr[count] = (wchar_t)arr[count];
>      }
> +    wstr[count] = 0;
>  
> -    wcstombs(name, wstr, len);
> +    dlen = wcstombs(NULL, wstr, 0) + 1;
> +    dest = g_malloc(dlen);
> +    wcstombs(dest, wstr, dlen);
>      g_free(wstr);
> +    return dest;
>  }
>  
>  /* Wrapper around write, returns 0 on failure */
> @@ -1703,7 +1709,7 @@ static void usb_mtp_write_metadata(MTPState *s)
>  {
>      MTPData *d = s->data_out;
>      ObjectInfo *dataset = (ObjectInfo *)d->data;
> -    char *filename = g_new0(char, dataset->length);
> +    char *filename;
>      MTPObject *o;
>      MTPObject *p = usb_mtp_object_lookup(s, s->dataset.parent_handle);
>      uint32_t next_handle = s->next_handle;
> @@ -1711,7 +1717,7 @@ static void usb_mtp_write_metadata(MTPState *s)
>      assert(!s->write_pending);
>      assert(p != NULL);
>  
> -    utf16_to_str(dataset->length, dataset->filename, filename);
> +    filename = utf16_to_str(dataset->length, dataset->filename);
>  
>      o = usb_mtp_object_lookup_name(p, filename, dataset->length);
>      if (o != NULL) {
>