linprocfs proc/pid/environ patch & list question

[Fernando Apesteguía]

2010/2/18 Kostik Belousov <kostikbel at gmail.com>:
> On Thu, Feb 18, 2010 at 06:48:35PM +0100, Fernando Apestegu?a wrote:
>> On Wed, Feb 17, 2010 at 8:11 PM, Kostik Belousov <kostikbel at gmail.com> wrote:
>> > On Wed, Feb 17, 2010 at 07:51:06PM +0100, Fernando Apestegu?a wrote:
>> >> Hi,
>> >>
>> >> I have a small patch (against 8.0-RELEASE-p2) that _should_ implement
>> >> the /proc/pid/environ file
>> >> under linprocfs.
>> >> However, it seems it does not work properly but I don't know what I'm
>> >> doing wrong.
>> >> Is this list the place to ask for help? I tried in the forums[1] but
>> >> got no answer.
>> > Putting aside any "does not work" questions, please see comment below.
>>
>> Sorry I didn't explain this. If I have a process forked from bash
>> shell in which I have
>> exported VAR=XXXX the /compat/linux/proc/pid/environ for the child process
>> does not show the VAR variable.
> Copyin copies the data from the address space of the current process.
> You are interested in the content of address space of different process.
> Look at the proc_rwmem().

Thanks

>
>>
>> >>
>> >> Don't we have a 'kernel newbies'-like list?
>> >>
>> >> Thanks in advance.
>> >>
>> >> [1] http://forums.freebsd.org/showthread.php?t=11329
>> >>
>> >> --- sys/compat/linprocfs/linprocfs.c.orig     2009-10-25 02:10:29.000000000 +0100
>> >> +++ sys/compat/linprocfs/linprocfs.c  2010-02-16 19:38:36.000000000 +0100
>> >> @@ -939,8 +939,38 @@
>> >>  static int
>> >>  linprocfs_doprocenviron(PFS_FILL_ARGS)
>> >>  {
>> >> +     int i, error;
>> >> +     struct ps_strings pss;
>> >> +     char **ps_envstr;
>> >>
>> >> -     sbuf_printf(sb, "doprocenviron\n%c", '\0');
>> >> +     PROC_LOCK(p);
>> >> +     if (p_cansee(td, p) != 0)
>> >> +             return (0);
>> >> +     PROC_UNLOCK(p);
>> >> +
>> >> +     error = copyin((void *)p->p_sysent->sv_psstrings, &pss,
>> >> +                                         sizeof(pss));
>> >> +     if (error)
>> >> +             return (error);
>> >> +
>> >> +     ps_envstr = malloc(pss.ps_nenvstr * sizeof(char *),
>> >> +         M_TEMP, M_WAITOK);
>> > This is essentially "panic me" code.  ps_nenvstr is user-controlled,
>> > and allows to specify arbitrary integers.
>> >
>> > Even ignoring exhaustion of the kernel map, it can cause allocation of
>> > big amount of physical memory. Note that execve(2) implementation uses
>> > swappable memory to store arguments and environment strings passed from
>> > vm spaces.
>>
>> Thanks for the comment. If I want to check ps_envstr, which threshold would be
>> reasonable? PAGE_SIZE maybe?
>>
>> Thanks again.
>>
>> >
>> >> +
>> >> +     error = copyin((void *)pss.ps_envstr, ps_envstr,
>> >> +         pss.ps_nenvstr * sizeof(char *));
>> >> +
>> >> +     if (error) {
>> >> +             free(ps_envstr, M_TEMP);
>> >> +             return (error);
>> >> +     }
>> >> +
>> >> +     /* NULL separated list of variable=value pairs */
>> >> +
>> >> +     for (i = 0; i < pss.ps_nenvstr; i++) {
>> >> +             sbuf_copyin(sb, ps_envstr[i], 0);
>> >> +     }
>> >> +
>> >> +     free(ps_envstr, M_TEMP);
>> >>       return (0);
>> >>  }
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>