amd64/187808: Pointer validation gone missing for __vdso_gettimeofday()

[Konstantin Belousov]

The following reply was made to PR amd64/187808; it has been noted by GNATS.

From: Konstantin Belousov <kostikbel at gmail.com>
To: Peter Holm <pho at freebsd.org>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: amd64/187808: Pointer validation gone missing for
 __vdso_gettimeofday()
Date: Fri, 21 Mar 2014 14:30:44 +0200

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 On Fri, Mar 21, 2014 at 09:26:26AM +0000, Peter Holm wrote:
 >=20
 > >Number:         187808
 > >Category:       amd64
 > >Synopsis:       Pointer validation gone missing for __vdso_gettimeofday()
 > >Confidential:   no
 > >Severity:       non-critical
 > >Priority:       low
 > >Responsible:    freebsd-amd64
 > >State:          open
 > >Quarter:       =20
 > >Keywords:      =20
 > >Date-Required:
 > >Class:          sw-bug
 > >Submitter-Id:   current-users
 > >Arrival-Date:   Fri Mar 21 09:30:00 UTC 2014
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     Peter Holm
 > >Release:        HEAD
 > >Organization:
 > >Environment:
 > FreeBSD t2.osted.lan 11.0-CURRENT FreeBSD 11.0-CURRENT #0 r263418M: Thu M=
 ar 20 07:20:51 CET 2014     pho at t2.osted.lan:/usr/src/sys/amd64/compile/PHO=
   amd64
 > >Description:
 > If first argument to gettimeofday() is an invalid pointer the call does n=
 ot return EFAULT.
 > >How-To-Repeat:
 > $ cat -n gettimeofday.c
 >      1  #include <err.h>
 >      2  #include <stdio.h>
 >      3  #include <sys/time.h>
 >      4  #include <sys/syscall.h>
 >      5  #include <unistd.h>
 >      6
 >      7  int
 >      8  main(void)
 >      9  {
 >     10          if (syscall(SYS_gettimeofday, (void *)-1, NULL) =3D=3D -1)
 >     11                  warn("syscall()");
 >     12
 >     13          /* broken by r237434 */
 >     14          if (gettimeofday((void *)-1, NULL) =3D=3D -1)
 >     15                  warn("gettimeofday()");
 >     16
 >     17          return (0);
 >     18  }
 > $ cc -o gettimeofday -Wall -Wextra -O2 -g gettimeofday.c
 > $ ./gettimeofday                                       =20
 > gettimeofday: syscall(): Bad address
 > Segmentation fault (core dumped)
 > $=20
 
 Nothing in the SUSvX requires the pointer to the struct timeval to be
 validated, or rather, if pointer is not valid, the behaviour is undefined.
 
 It is impossible to 'fix' this in reliable manner for userspace function.
 The expectations are the same as for other functions, e.g. strcmp(3).
 
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