Date: Wed, 12 Dec 2001 10:36:03 -0500 (EST) From: Mike Heffner <mheffner@vt.edu> To: Peter Pentchev <roam@ringlet.net> Cc: FreeBSD-bugs <freebsd-bugs@freebsd.org>, Marc Olzheim <marcolz@ilse.nl>, freebsd-gnats-submit@freebsd.org Subject: Re: bin/19422: users can overflow argv to make ps segfault Message-ID: <XFMail.20011212103603.mheffner@vt.edu> In-Reply-To: <20011212115039.B934@straylight.oblivion.bg>
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On 12-Dec-2001 Peter Pentchev wrote:
| On Tue, Dec 11, 2001 at 11:18:54PM -0500, Mike Heffner wrote:
|>
|> Well, I've looked at this a little more. I was able to reproduce it (it
|> took a few times though). Unfortunately, the patch isn't as simple as
|> the
|> one in the PR. Could you please try the attached patch? There is still
|> a
|> problem though, and that is that the strlen()s can seg. fault if the
|> argv[] strings aren't NULL terminated - I don't know how to fix this
|> problem though :(
|
| If argv[] is the program arguments' array, as passed to main(), then
| you should not worry about it - its elements are supposed to be proper
| C strings, i.e. terminated by a '\0' character, and I still have to see
| a platform where they are not :)
But when a user modifies those arguments by explicilty setting argv[0], or
whatever, is where the problem is:
test5.c:
#include <stdio.h>
#include <sys/exec.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/types.h>
#include <unistd.h>
int
main(int argc, char *argv[])
{
int oid[4];
char before[] = "BBBBBBB";
char after[5];
memset(after, 'A', sizeof(after));
argv[0] = after;
oid[0] = CTL_KERN;
oid[1] = KERN_PROC;
oid[2] = KERN_PROC_ARGS;
oid[3] = getpid();
sysctl(oid, 4, 0, 0, after, 65537);
sleep(600);
return(0);
}
$ ./test5
on another terminal:
$ ps auxwww
...
spock 290 0.0 0.3 980 109 p0 S+ 10:30AM 0:00.01 \
AAAAA\M-{\M-?\M-?BBBBBBB (test5)
^^^^^^^^^^^^^^^^^^^
Mike
--
Mike Heffner <mheffner@[acm.]vt.edu>
Blacksburg, VA <mikeh@FreeBSD.org>
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