linprocfs proc/pid/environ patch & list question
Fernando Apesteguía
fernando.apesteguia at gmail.com
Thu Feb 18 17:48:36 UTC 2010
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.
>>
>> 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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