Re: [PATCH v4] linux: Fix ancillary 64-bit time timestamp conversion (BZ #28349, BZ #28350)

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

I wrongly pushed this upstream and I will revert it.

Sorry about the noise.

On 22/12/2021 15:52, Adhemerval Zanella wrote:
> The __convert_scm_timestamps() only updates the control message last
> pointer for SOL_SOCKET type, so if the message control buffer contains
> multiple ancillary message types the converted timestamp one might
> overwrite a valid message.
> 
> The test check if the extra ancillary space is correctly handled
> by recvmsg/recvmmsg, where if there is no extra space for the 64-bit
> time_t converted message the control buffer should be marked with
> MSG_TRUNC.  It also check if recvmsg/recvmmsg handle correctly multiple
> ancillary data.
> 
> Checked on x86_64-linux and on i686-linux-gnu on both 5.11 and
> 4.15 kernel.
> 
> Co-authored-by: Fabian Vogt <fvogt@suse.de>
> ---
> v3: Fix unitilized data usage by CMSG_NXTHDR [1]
> 
> [1] https://patchwork.sourceware.org/project/glibc/patch/7960950.1uK8C5oMiK@linux-e202.suse.de/ 
> ---
>  sysdeps/unix/sysv/linux/Makefile              |   3 +
>  .../unix/sysv/linux/convert_scm_timestamps.c  |  11 +-
>  .../sysv/linux/tst-socket-timestamp-time64.c  |   1 +
>  .../unix/sysv/linux/tst-socket-timestamp.c    | 344 ++++++++++++++++++
>  4 files changed, 354 insertions(+), 5 deletions(-)
>  create mode 100644 sysdeps/unix/sysv/linux/tst-socket-timestamp-time64.c
>  create mode 100644 sysdeps/unix/sysv/linux/tst-socket-timestamp.c
> 
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 61acc1987d..60aa9d89d6 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -275,6 +275,9 @@ sysdep_routines += cmsg_nxthdr
>  CFLAGS-recvmmsg.c = -fexceptions -fasynchronous-unwind-tables
>  CFLAGS-sendmmsg.c = -fexceptions -fasynchronous-unwind-tables
>  
> +tests += tst-socket-timestamp
> +tests-time64 += tst-socket-timestamp-time64
> +
>  tests-special += $(objpfx)tst-socket-consts.out
>  $(objpfx)tst-socket-consts.out: ../sysdeps/unix/sysv/linux/tst-socket-consts.py
>  	PYTHONPATH=../scripts \
> diff --git a/sysdeps/unix/sysv/linux/convert_scm_timestamps.c b/sysdeps/unix/sysv/linux/convert_scm_timestamps.c
> index 00c934c413..36976c276f 100644
> --- a/sysdeps/unix/sysv/linux/convert_scm_timestamps.c
> +++ b/sysdeps/unix/sysv/linux/convert_scm_timestamps.c
> @@ -54,6 +54,8 @@ __convert_scm_timestamps (struct msghdr *msg, socklen_t msgsize)
>         cmsg != NULL;
>         cmsg = CMSG_NXTHDR (msg, cmsg))
>      {
> +      last = cmsg;
> +
>        if (cmsg->cmsg_level != SOL_SOCKET)
>  	continue;
>  
> @@ -75,8 +77,6 @@ __convert_scm_timestamps (struct msghdr *msg, socklen_t msgsize)
>  	  tvts[1] = tmp[1];
>  	  break;
>  	}
> -
> -      last = cmsg;
>      }
>  
>    if (last == NULL || type == 0)
> @@ -88,10 +88,11 @@ __convert_scm_timestamps (struct msghdr *msg, socklen_t msgsize)
>        return;
>      }
>  
> +  /* Zero memory for the new cmsghdr, required by CMSG_NXTHDR.  */
> +  memset (msg->msg_control + msg->msg_controllen, 0,
> +	  CMSG_SPACE (sizeof tvts));
>    msg->msg_controllen += CMSG_SPACE (sizeof tvts);
> -  cmsg = CMSG_NXTHDR(msg, last);
> -  if (cmsg == NULL)
> -    return;
> +  cmsg = CMSG_NXTHDR (msg, last);
>    cmsg->cmsg_level = SOL_SOCKET;
>    cmsg->cmsg_type = type;
>    cmsg->cmsg_len = CMSG_LEN (sizeof tvts);
> diff --git a/sysdeps/unix/sysv/linux/tst-socket-timestamp-time64.c b/sysdeps/unix/sysv/linux/tst-socket-timestamp-time64.c
> new file mode 100644
> index 0000000000..ae424c2a70
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-socket-timestamp-time64.c
> @@ -0,0 +1 @@
> +#include "tst-socket-timestamp.c"
> diff --git a/sysdeps/unix/sysv/linux/tst-socket-timestamp.c b/sysdeps/unix/sysv/linux/tst-socket-timestamp.c
> new file mode 100644
> index 0000000000..3854c46bad
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-socket-timestamp.c
> @@ -0,0 +1,344 @@
> +/* Check recvmsg/recvmmsg 64-bit timestamp support.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <array_length.h>
> +#include <arpa/inet.h>
> +#include <errno.h>
> +#include <string.h>
> +#include <stdio.h>
> +#include <support/check.h>
> +#include <support/next_to_fault.h>
> +#include <support/support.h>
> +#include <support/test-driver.h>
> +#include <support/xunistd.h>
> +#include <support/xsocket.h>
> +#include <sys/mman.h>
> +
> +/* Some extra space added for ancillary data, it might be used to convert
> +   32-bit timestamp to 64-bit for _TIME_BITS=64.  */
> +enum { slack_max_size = 64 };
> +static const int slack[] = { 0, 4, 8, 16, 32, slack_max_size };
> +
> +static bool support_64_timestamp;
> +/* AF_INET socket and address used to send and receive data.  */
> +static int srv;
> +static struct sockaddr_in srv_addr;
> +
> +static int
> +do_sendto (const struct sockaddr_in *addr, int nmsgs)
> +{
> +  int s = xsocket (AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
> +  xconnect (s, (const struct sockaddr *) addr, sizeof (*addr));
> +
> +  for (int i = 0; i < nmsgs; i++)
> +    xsendto (s, &i, sizeof (i), 0, (const struct sockaddr *) addr,
> +	     sizeof (*addr));
> +
> +  return 0;
> +}
> +
> +static void
> +do_recvmsg_slack_ancillary (bool use_multi_call, int s, void *cmsg,
> +			    size_t slack, size_t tsize, int exp_msg)
> +{
> +  int msg;
> +  struct iovec iov =
> +    {
> +      .iov_base = &msg,
> +      .iov_len = sizeof (msg)
> +    };
> +  size_t msg_controllen = CMSG_SPACE (tsize) + slack;
> +  char *msg_control = cmsg - msg_controllen;
> +  memset (msg_control, 0x55, msg_controllen);
> +  struct mmsghdr mmhdr =
> +    {
> +      .msg_hdr =
> +      {
> +        .msg_name = NULL,
> +        .msg_namelen = 0,
> +        .msg_iov = &iov,
> +        .msg_iovlen = 1,
> +        .msg_control = msg_control,
> +        .msg_controllen = msg_controllen
> +      },
> +    };
> +
> +  int r;
> +  if (use_multi_call)
> +    {
> +      r = recvmmsg (s, &mmhdr, 1, 0, NULL);
> +      if (r >= 0)
> +	r = mmhdr.msg_len;
> +    }
> +  else
> +    r = recvmsg (s, &mmhdr.msg_hdr, 0);
> +  TEST_COMPARE (r, sizeof (int));
> +  TEST_COMPARE (msg, exp_msg);
> +
> +  if (cmsg == NULL)
> +    return;
> +
> +  /* A timestamp is expected if 32-bit timestamp are used (support in every
> +     configuration) or if underlying kernel support 64-bit timestamps.
> +     Otherwise recvmsg will need extra space do add the 64-bit timestamp.  */
> +  bool exp_timestamp;
> +  if (sizeof (time_t) == 4 || support_64_timestamp)
> +    exp_timestamp = true;
> +   else
> +    exp_timestamp = slack >= CMSG_SPACE (tsize);
> +
> +  bool timestamp = false;
> +  for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
> +       cmsg != NULL;
> +       cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
> +    {
> +      if (cmsg->cmsg_level != SOL_SOCKET)
> +	continue;
> +      if (cmsg->cmsg_type == SCM_TIMESTAMP
> +	  && cmsg->cmsg_len == CMSG_LEN (sizeof (struct timeval)))
> +	{
> +	  struct timeval tv;
> +	  memcpy (&tv, CMSG_DATA (cmsg), sizeof (tv));
> +	  if (test_verbose)
> +	    printf ("SCM_TIMESTAMP:   {%jd, %jd}\n", (intmax_t)tv.tv_sec,
> +		    (intmax_t)tv.tv_usec);
> +	  timestamp = true;
> +	}
> +      else if (cmsg->cmsg_type == SCM_TIMESTAMPNS
> +	       && cmsg->cmsg_len == CMSG_LEN (sizeof (struct timespec)))
> +	{
> +	  struct timespec ts;
> +	  memcpy (&ts, CMSG_DATA (cmsg), sizeof (ts));
> +	  if (test_verbose)
> +	    printf ("SCM_TIMESTAMPNS: {%jd, %jd}\n", (intmax_t)ts.tv_sec,
> +		    (intmax_t)ts.tv_nsec);
> +	  timestamp = true;
> +	}
> +    }
> +
> +  /* If there is not timestamp in the ancilliary data, recvmsg should set
> +     the flag inidcating it.  */
> +  if (exp_timestamp && !timestamp)
> +    TEST_VERIFY (mmhdr.msg_hdr.msg_flags & MSG_TRUNC);
> +  else
> +    TEST_COMPARE (timestamp, exp_timestamp);
> +}
> +
> +/* Check if the extra ancillary space is correctly handled by recvmsg and
> +   recvmmsg: if there is no extra space for the 64-bit timestamp the syscall
> +   should set MSG_TRUNC flag, otherwise an extra cmsghdr with the converted
> +   timestamp is appended at the message control buffer.  */
> +static void
> +do_test_slack_space (void)
> +{
> +  /* Setup the ancillary data buffer with an extra page with PROT_NONE to
> +     check the possible timestamp conversion on some systems.  */
> +  struct support_next_to_fault nf =
> +    support_next_to_fault_allocate (slack_max_size);
> +  void *msgbuf = nf.buffer + slack_max_size;
> +
> +  /* Enable the timestamp using struct timeval precision.  */
> +  {
> +    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMP, &(int){1},
> +			sizeof (int));
> +    TEST_VERIFY_EXIT (r != -1);
> +  }
> +  /* Check recvmsg.  */
> +  do_sendto (&srv_addr, array_length (slack));
> +  for (int s = 0; s < array_length (slack); s++) {
> +    memset (nf.buffer, 0x55, nf.length);
> +    do_recvmsg_slack_ancillary (false, srv, msgbuf, slack[s],
> +				sizeof (struct timeval), s);
> +  }
> +  /* Check recvmmsg.  */
> +  do_sendto (&srv_addr, array_length (slack));
> +  for (int s = 0; s < array_length (slack); s++) {
> +    memset (nf.buffer, 0x55, nf.length);
> +    do_recvmsg_slack_ancillary (true, srv, msgbuf, slack[s],
> +				sizeof (struct timeval), s);
> +  }
> +
> +  /* Now enable timestamp using a higher precision, it overwrites the previous
> +     precision.  */
> +  {
> +    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMPNS, &(int){1},
> +			sizeof (int));
> +    TEST_VERIFY_EXIT (r != -1);
> +  }
> +  /* Check recvmsg.  */
> +  do_sendto (&srv_addr, array_length (slack));
> +  for (int s = 0; s < array_length (slack); s++)
> +    do_recvmsg_slack_ancillary (false, srv, msgbuf, slack[s],
> +				sizeof (struct timespec), s);
> +  /* Check recvmmsg.  */
> +  do_sendto (&srv_addr, array_length (slack));
> +  for (int s = 0; s < array_length (slack); s++)
> +    do_recvmsg_slack_ancillary (true, srv, msgbuf, slack[s],
> +				sizeof (struct timespec), s);
> +
> +  support_next_to_fault_free (&nf);
> +}
> +
> +/* Check if the converted 64-bit timestamp is correctly appended when there
> +   are multiple ancillary messages.  */
> +static void
> +do_recvmsg_multiple_ancillary (bool use_multi_call, int s, void *cmsg,
> +			       size_t cmsgsize, int exp_msg)
> +{
> +  int msg;
> +  struct iovec iov =
> +    {
> +      .iov_base = &msg,
> +      .iov_len = sizeof (msg)
> +    };
> +  size_t msgs = cmsgsize;
> +  struct mmsghdr mmhdr =
> +    {
> +      .msg_hdr =
> +      {
> +        .msg_name = NULL,
> +        .msg_namelen = 0,
> +        .msg_iov = &iov,
> +        .msg_iovlen = 1,
> +        .msg_controllen = msgs,
> +        .msg_control = cmsg,
> +      },
> +    };
> +
> +  int r;
> +  if (use_multi_call)
> +    {
> +      r = recvmmsg (s, &mmhdr, 1, 0, NULL);
> +      if (r >= 0)
> +	r = mmhdr.msg_len;
> +    }
> +  else
> +    r = recvmsg (s, &mmhdr.msg_hdr, 0);
> +  TEST_COMPARE (r, sizeof (int));
> +  TEST_COMPARE (msg, exp_msg);
> +
> +  if (cmsg == NULL)
> +    return;
> +
> +  bool timestamp = false;
> +  bool origdstaddr = false;
> +  for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
> +       cmsg != NULL;
> +       cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
> +    {
> +      if (cmsg->cmsg_level == SOL_IP
> +	  && cmsg->cmsg_type == IP_ORIGDSTADDR
> +	  && cmsg->cmsg_len >= CMSG_LEN (sizeof (struct sockaddr_in)))
> +	{
> +	  struct sockaddr_in sa;
> +	  memcpy (&sa, CMSG_DATA (cmsg), sizeof (sa));
> +	  if (test_verbose)
> +	    {
> +	      char str[INET_ADDRSTRLEN];
> +	      inet_ntop (AF_INET, &sa.sin_addr, str, INET_ADDRSTRLEN);
> +	      printf ("IP_ORIGDSTADDR:  %s:%d\n", str, ntohs (sa.sin_port));
> +	    }
> +	  origdstaddr = sa.sin_addr.s_addr == srv_addr.sin_addr.s_addr
> +			&& sa.sin_port == srv_addr.sin_port;
> +	}
> +      if (cmsg->cmsg_level == SOL_SOCKET
> +	  && cmsg->cmsg_type == SCM_TIMESTAMP
> +	  && cmsg->cmsg_len >= CMSG_LEN (sizeof (struct timeval)))
> +	{
> +	  struct timeval tv;
> +	  memcpy (&tv, CMSG_DATA (cmsg), sizeof (tv));
> +	  if (test_verbose)
> +	    printf ("SCM_TIMESTAMP:   {%jd, %jd}\n", (intmax_t)tv.tv_sec,
> +		    (intmax_t)tv.tv_usec);
> +	  timestamp = true;
> +	}
> +    }
> +
> +  /* If there is no timestamp in the ancillary data, recvmsg should set
> +     the flag to indicate it.  */
> +  if (!timestamp)
> +    TEST_VERIFY (mmhdr.msg_hdr.msg_flags & MSG_TRUNC);
> +  else
> +    TEST_COMPARE (timestamp, true);
> +  TEST_COMPARE (origdstaddr, true);
> +}
> +
> +static void
> +do_test_multiple_ancillary (void)
> +{
> +  {
> +    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMP, &(int){1},
> +			sizeof (int));
> +    TEST_VERIFY_EXIT (r != -1);
> +  }
> +  {
> +    int r = setsockopt (srv, IPPROTO_IP, IP_RECVORIGDSTADDR, &(int){1},
> +			sizeof (int));
> +    TEST_VERIFY_EXIT (r != -1);
> +  }
> +
> +  /* Enougth data for default SO_TIMESTAMP, the IP_RECVORIGDSTADDR, and the
> +     extra 64-bit SO_TIMESTAMP.  */
> +  enum { msgbuflen = CMSG_SPACE (2 * sizeof (uint64_t))
> +		     + CMSG_SPACE (sizeof (struct sockaddr_in))
> +		     + CMSG_SPACE (2 * sizeof (uint64_t)) };
> +  char msgbuf[msgbuflen];
> +
> +  enum { nmsgs = 8 };
> +  /* Check recvmsg.  */
> +  do_sendto (&srv_addr, nmsgs);
> +  for (int s = 0; s < nmsgs; s++)
> +    do_recvmsg_multiple_ancillary (false, srv, msgbuf, msgbuflen, s);
> +  /* Check recvmmsg.  */
> +  do_sendto (&srv_addr, nmsgs);
> +  for (int s = 0; s < nmsgs; s++)
> +    do_recvmsg_multiple_ancillary (true, srv, msgbuf, msgbuflen, s);
> +}
> +
> +static int
> +do_test (void)
> +{
> +  srv = xsocket (AF_INET, SOCK_DGRAM, 0);
> +  srv_addr = (struct sockaddr_in) {
> +    .sin_family = AF_INET,
> +    .sin_addr = {.s_addr = htonl (INADDR_LOOPBACK) },
> +  };
> +  xbind (srv, (struct sockaddr *) &srv_addr, sizeof (srv_addr));
> +  {
> +    socklen_t sa_len = sizeof (srv_addr);
> +    xgetsockname (srv, (struct sockaddr *) &srv_addr, &sa_len);
> +    TEST_VERIFY (sa_len == sizeof (srv_addr));
> +  }
> +
> +  TEST_COMPARE (recvmsg (-1, NULL, 0), -1);
> +  TEST_COMPARE (errno, EBADF);
> +  TEST_COMPARE (recvmmsg (-1, NULL, 0, 0, NULL), -1);
> +  TEST_COMPARE (errno, EBADF);
> +
> +  /* If underlying kernel does not support   */
> +  support_64_timestamp = support_socket_so_timestamp_time64 (srv);
> +
> +  do_test_slack_space ();
> +  do_test_multiple_ancillary ();
> +
> +  xclose (srv);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>