Re: Build problems in kdd.c with xen-4.14.0-rc4

[Wei Liu <wl@xxxxxxx>]

On Fri, Jul 03, 2020 at 07:54:57PM +0100, Tim Deegan wrote:
> Hi Michael,
> 
> Thanks for ther report!
> 
> At 23:21 +0100 on 30 Jun (1593559296), Michael Young wrote:
> > I get the following errors when trying to build xen-4.14.0-rc4
> > 
> > kdd.c: In function 'kdd_tx':
> > kdd.c:754:15: error: array subscript 16 is above array bounds of 
> > 'uint8_t[16]' {aka 'unsigned char[16]'} [-Werror=array-bounds]
> >    754 |         s->txb[len++] = 0xaa;
> >        |         ~~~~~~^~~~~~~
> > kdd.c:82:17: note: while referencing 'txb'
> >     82 |         uint8_t txb[sizeof (kdd_hdr)];           /* Marshalling 
> > area for tx */
> >        |                 ^~~
> > kdd.c: In function 'kdd_break':
> > kdd.c:819:19: error: array subscript 16 is above array bounds of 
> > 'uint8_t[16]' {aka 'unsigned char[16]'} [-Werror=array-bounds]
> 
> Oh dear.  The fix for the last kdd bug seems to have gone wrong
> somewhere.  The patch I posted has:
> 
> -        uint8_t txb[sizeof (kdd_hdr) + 65536];   /* Marshalling area for tx 
> */
> +        uint8_t txb[sizeof (kdd_pkt)];           /* Marshalling area for tx 
> */
> 
> but as applied in master it's:
> 
> -        uint8_t txb[sizeof (kdd_hdr) + 65536];   /* Marshalling area for tx 
> */
> +        uint8_t txb[sizeof (kdd_hdr)];           /* Marshalling area for tx 
> */
> 
> i.e. the marshalling area is only large enough for a header and GCC
> is correctly complaining about that.
> 
> Wei, it looks like you committed this patch - can you figure out what
> happened to it please?
> 

My bad. The mail I saved did not apply cleanly so I manually recreated
your patch.

Thanks for letting me know. I will send a patch to fix the issue.

Wei.

> Cheers,
> 
> Tim.