Crash in sendto_kdc.c

Greg Hudson ghudson at
Thu Oct 4 16:01:13 EDT 2018

[Removing kfwdev from the CC line; we no longer have a separate Windows 
development team, so just krbdev is fine.]

On 10/04/2018 08:47 AM, wrote:
> conn.out.sgbuf[0] = {len = 4, buff = ‘\0’}
> conn.out.sgbuf[1] = {len = 1882, buff = ‘some data’}
> conn.out.sgp = {len=??? buf=??? }
> conn.out.sg_count = -10339
> conn.out.msg_len_buf = ""
> nwritten = 3199132154

Thanks for the additional information.  I think I finally know what is 
going wrong here: SOCKET_WRITEV() is trying to return -1, but due to the 
intricacies of the C type system, it is being treated as 2^32-1 on 
64-bit Windows.

The fix I would like to try is to edit src/include/port-sockets.h and 
change the first definition of SOCKET_WRITEV to:

#define SOCKET_WRITEV(FD, SG, LEN, TMP)                         \
     (WSASend((FD), (SG), (LEN), &(TMP), 0, 0, 0) ?              \
      (ssize_t)-1 : (ssize_t)(TMP))

where the change is the addition of the (ssize_t) casts.

Without the casts, the type of the conditional expression is unsigned 
32-bit, because -1 has type int and TMP has type DWORD, and unsigned 
wins over signed for integer types of equal size.  The quantity -1 in 
that type has the value 2^32-1.  When that value is cast to ssize_t 
(signed 64-bit on 64-bit Windows), it retains the large positive value 
instead of reverting back to -1 as it would on 32-bit Windows.

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