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Cygwin: AF_UNIX: evaluate_cmsg_data: improve error handling

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Set msg_controllen to the number of bytes of ancillary data actually
copied to msg_control.

Set the MSG_CTRUNC flag when appropriate.
This commit is contained in:
Ken Brown 2020-10-27 14:25:00 -04:00
parent 82474332a6
commit 3ef34ca308
1 changed files with 31 additions and 13 deletions
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40
winsup/cygwin/fhandler_socket_unix.cc
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@ -1942,24 +1942,42 @@ bool
fhandler_socket_unix::evaluate_cmsg_data (af_unix_pkt_hdr_t *packet,
struct msghdr *msg, bool cloexec)
{
if (packet->cmsg_len != CMSG_SPACE (sizeof (struct ucred))
|| msg->msg_controllen < packet->cmsg_len)
/* FIXME: What errno should we set? For example, if
packet->cmsg_len == 0, then we were expecting ancillary data
but didn't get any. */
return false;
if (!msg->msg_control
|| msg->msg_controllen < (int) CMSG_SPACE (sizeof (struct ucred)))
{
/* Discard ancillary data. */
msg->msg_flags |= MSG_CTRUNC;
msg->msg_controllen = 0;
return true;
}
struct cmsghdr *cmsg = AF_UNIX_PKT_CMSG (packet);
if (!cmsg || cmsg->cmsg_len != CMSG_LEN (sizeof (struct ucred))
if (cmsg->cmsg_len != CMSG_LEN (sizeof (struct ucred))
|| cmsg->cmsg_level != SOL_SOCKET
|| cmsg->cmsg_type != SCM_CREDENTIALS)
/* FIXME: What errno should we set? */
/* FIXME: Is this the right errno? */
{
set_errno (EOPNOTSUPP);
msg->msg_controllen = 0;
return false;
}
/* FIXME: Is this right? Do we just do nothing with no error
indication? Or should we return false, causing recvmsg to fail?
In that case what errno should we set? */
indication other than setting msg_controllen = 0? Or should we
return false, causing recvmsg to fail? In that case what errno
should we set? */
if (!so_passcred ())
{
msg-> msg_controllen = 0;
return true;
memcpy (msg->msg_control, AF_UNIX_PKT_CMSG (packet), packet->cmsg_len);
}
if (packet->cmsg_len > CMSG_SPACE (sizeof (struct ucred)))
/* FIXME: We're discarding some data, but not for the reasons
specified at
https://man7.org/linux/man-pages/man2/recvmsg.2.html. Do we
still set MSG_CTRUNC? */
msg->msg_flags |= MSG_CTRUNC;
memcpy (msg->msg_control, AF_UNIX_PKT_CMSG (packet),
CMSG_LEN (sizeof (struct ucred)));
msg->msg_controllen = CMSG_LEN (sizeof (struct ucred));
return true;
}