[PATCH] Cygwin: Allow to set SO_PEERCRED zero
Corinna Vinschen
corinna-cygwin@cygwin.com
Mon Dec 7 09:36:03 GMT 2020
Hi Mark,
On Dec 6 22:28, Mark Geisert wrote:
> The existing code errors as EINVAL any attempt to set a value for
> SO_PEERCRED via setsockopt() on an AF_UNIX/AF_LOCAL socket. But to
> enable the workaround set_no_getpeereid behavior for Python one has
> to be able to set SO_PEERCRED to zero. Ergo, this patch. Python has
> no way to specify a NULL pointer for 'optval'.
>
> ---
> winsup/cygwin/fhandler_socket_local.cc | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/winsup/cygwin/fhandler_socket_local.cc b/winsup/cygwin/fhandler_socket_local.cc
> index c94bf828f..421b8bbdb 100644
> --- a/winsup/cygwin/fhandler_socket_local.cc
> +++ b/winsup/cygwin/fhandler_socket_local.cc
> @@ -1430,7 +1430,8 @@ fhandler_socket_local::setsockopt (int level, int optname, const void *optval,
> FIXME: In the long run we should find a more generic solution
> which doesn't require a blocking handshake in accept/connect
> to exchange SO_PEERCRED credentials. */
> - if (optval || optlen)
> + /* Temporary: Allow only '(int) 0' to be specified. */
> + if (optlen < (socklen_t) sizeof (int) || 0 != *(int *) optval)
> set_errno (EINVAL);
That breaks existing callers calling setsockopt like this:
setsockopt (fd, SOL_SOCKET, SO_PEERCRED, NULL, 0);
This should stay backward-compatible. It should allow the above
as well as your int usage, otherwise postfix will stop working.
Also, please write either
*(int *) optval != 0
or just
!!*(int *) optval
Thanks,
Corinna
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