netdev - [PATCH] net: support compat 64-bit time in {s,g}etsockopt

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Date:   Wed, 25 Apr 2018 10:21:54 -0400
From:   Lance Richardson <lance.richardson.net@...il.com>
To:     netdev@...r.kernel.org
Cc:     gopalsr83@...il.com, vapier@...omium.org, hjl.tools@...il.com
Subject: [PATCH] net: support compat 64-bit time in {s,g}etsockopt

For the x32 ABI, struct timeval has two 64-bit fields. However
the kernel currently interprets the user-space values used for
the SO_RCVTIMEO and SO_SNDTIMEO socket options as having a pair
of 32-bit fields.

When the seconds portion of the requested timeout is less than 2**32,
the seconds portion of the effective timeout is correct but the
microseconds portion is zero.  When the seconds portion of the
requested timeout is zero and the microseconds portion is non-zero,
the kernel interprets the timeout as zero (never timeout).

Fix by using 64-bit time for SO_RCVTIMEO/SO_SNDTIMEO as required
for the ABI.

The code included below demonstrates the problem.

Results before patch:
    $ gcc -m64 -Wall -O2 -o socktmo socktmo.c && ./socktmo
    recv time: 2.008181 seconds
    send time: 2.015985 seconds

    $ gcc -m32 -Wall -O2 -o socktmo socktmo.c && ./socktmo
    recv time: 2.016763 seconds
    send time: 2.016062 seconds

    $ gcc -mx32 -Wall -O2 -o socktmo socktmo.c && ./socktmo
    recv time: 1.007239 seconds
    send time: 1.023890 seconds

Results after patch:
    $ gcc -m64 -O2 -Wall -o socktmo socktmo.c && ./socktmo
    recv time: 2.010062 seconds
    send time: 2.015836 seconds

    $ gcc -m32 -O2 -Wall -o socktmo socktmo.c && ./socktmo
    recv time: 2.013974 seconds
    send time: 2.015981 seconds

    $ gcc -mx32 -O2 -Wall -o socktmo socktmo.c && ./socktmo
    recv time: 2.030257 seconds
    send time: 2.013383 seconds

 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/time.h>

 void checkrc(char *str, int rc)
 {
         if (rc >= 0)
                 return;

         perror(str);
         exit(1);
 }

 static char buf[1024];
 int main(int argc, char **argv)
 {
         int rc;
         int socks[2];
         struct timeval tv;
         struct timeval start, end, delta;

         rc = socketpair(AF_UNIX, SOCK_STREAM, 0, socks);
         checkrc("socketpair", rc);

         /* set timeout to 1.999999 seconds */
         tv.tv_sec = 1;
         tv.tv_usec = 999999;
         rc = setsockopt(socks[0], SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof tv);
         rc = setsockopt(socks[0], SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof tv);
         checkrc("setsockopt", rc);

         /* measure actual receive timeout */
         gettimeofday(&start, NULL);
         rc = recv(socks[0], buf, sizeof buf, 0);
         gettimeofday(&end, NULL);
         timersub(&end, &start, &delta);

         printf("recv time: %ld.%06ld seconds\n",
                (long)delta.tv_sec, (long)delta.tv_usec);

         /* fill send buffer */
         do {
                 rc = send(socks[0], buf, sizeof buf, 0);
         } while (rc > 0);

         /* measure actual send timeout */
         gettimeofday(&start, NULL);
         rc = send(socks[0], buf, sizeof buf, 0);
         gettimeofday(&end, NULL);
         timersub(&end, &start, &delta);

         printf("send time: %ld.%06ld seconds\n",
                (long)delta.tv_sec, (long)delta.tv_usec);
         exit(0);
 }

Fixes: 515c7af85ed9 ("x32: Use compat shims for {g,s}etsockopt")
Reported-by: Gopal RajagopalSai <gopalsr83@...il.com>
Signed-off-by: Lance Richardson <lance.richardson.net@...il.com>
---
 net/compat.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/compat.c b/net/compat.c
index 5ae7437d3853..7242cce5631b 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -377,7 +377,8 @@ static int compat_sock_setsockopt(struct socket *sock, int level, int optname,
 	    optname == SO_ATTACH_REUSEPORT_CBPF)
 		return do_set_attach_filter(sock, level, optname,
 					    optval, optlen);
-	if (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO)
+	if (!COMPAT_USE_64BIT_TIME &&
+	    (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO))
 		return do_set_sock_timeout(sock, level, optname, optval, optlen);
 
 	return sock_setsockopt(sock, level, optname, optval, optlen);
@@ -448,7 +449,8 @@ static int do_get_sock_timeout(struct socket *sock, int level, int optname,
 static int compat_sock_getsockopt(struct socket *sock, int level, int optname,
 				char __user *optval, int __user *optlen)
 {
-	if (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO)
+	if (!COMPAT_USE_64BIT_TIME &&
+	    (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO))
 		return do_get_sock_timeout(sock, level, optname, optval, optlen);
 	return sock_getsockopt(sock, level, optname, optval, optlen);
 }
-- 
2.11.0