Re: [qemu-s390x] [Qemu-devel] [PATCH 10/14] usb-mtp: avoid warning about unaligned access to filename

[Peter Maydell]

On Fri, 29 Mar 2019 at 11:22, Daniel P. Berrangé <address@hidden> wrote:
>
> The 'filename' field in ObjectInfo struct is declared as a
> zero length array of uint16_t. Accessing it is equivalent
> to taking the address of the field, and taking the address
> of fields in a packed struct causes unaligned pointer
> warnings:
>
> hw/usb/dev-mtp.c: In function ‘usb_mtp_write_metadata’:
> hw/usb/dev-mtp.c:1712:36: warning: taking address of packed member of ‘struct 
> <anonymous>’ may result in an unaligned pointer value 
> [-Waddress-of-packed-member]
>  1712 |                             dataset->filename);
>       |                             ~~~~~~~^~~~~~~~~~

This one's come up before -- see
http://patchwork.ozlabs.org/patch/1049654/
and my comments on it. I think that utf16_to_str()
should take a byte array and use the appropriate
lduw_*_p() function to read from it, and that we
need to think more carefully about endianness and
about the "malicious short buffer" case.

thanks
-- PMM