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

[Paul Durrant <xadimgnik@gmail.com>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of Michael Young
> Sent: 30 June 2020 23:22
> To: xen-devel@lists.xenproject.org
> Cc: Tim Deegan <tim@xen.org>
> Subject: Build problems in kdd.c with xen-4.14.0-rc4
> 
> 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]
>    819 |             s->txb[sizeof (kdd_hdr) + i] = i;
>        |             ~~~~~~^~~~~~~~~~~~~~~~~~~~~~
> kdd.c:82:17: note: while referencing 'txb'
>     82 |         uint8_t txb[sizeof (kdd_hdr)];           /* Marshalling area for tx */
>        |                 ^~~
> In file included from /usr/include/stdio.h:867,
>                   from kdd.c:36:
> In function 'vsnprintf',
>      inlined from 'kdd_send_string' at kdd.c:791:11:
> /usr/include/bits/stdio2.h:80:10: error: '__builtin___vsnprintf_chk' specified bound 65519 exceeds
> destination size 0 [-Werror=stringop-overflow=]
>     80 |   return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>        |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     81 |         __bos (__s), __fmt, __ap);
>        |         ~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[4]: *** [/builddir/build/BUILD/xen-4.14.0-rc4/tools/debugger/kdd/../../../tools/Rules.mk:216:
> kdd.o] Error 1
> 
> The first two array-bounds errors seem to be a result of the
> 
> kdd: stop using [0] arrays to access packet contents
> 
> patch at
> http://xenbits.xenproject.org/gitweb/?p=xen.git;a=commit;h=3471cafbdda35eacf04670881dd2aee2558b4f08
> 
> which reduced the size of txb from
> sizeof (kdd_hdr) + 65536
> to
> sizeof (kdd_hdr)
> which means the code now tries to write beyond the end of txb in both
> cases.
> 

Sorry not to get back to you sooner. Which compiler are you using?

  Paul

>  	Michael Young