On Fri, 21 Jan 2000, Sergey Kubushin wrote:
> Hi, everybody!
>
> I have a question about fork() (?) behaviour. The problem shows itself as
> truncated lines in ps output on processes that are forked outta daemons
> which use setproctitle() (from sendmail sources) such as sendmail, inetd
> etc. All's fine on 2.2.xx kernels, but I have the following under 2.3.xx :
>
> === Cut ===
> 22352 ? S 0:00 sendmail: accepting connectio
> 22353 ? S 0:00 \_ sendmail: LAA14150 relay1.cha
> .
> .
> .
> 701 ? S 0:13 inetd
> 2765 ? S 0:01 \_ ftpd: 19
> 5294 ? S 0:00 \_ ftpd: sa
> 13547 ? S 0:00 \_ ftpd: fi
> 14656 ? S 0:00 \_ ftpd: 19
> 14760 ? S 0:00 \_ ftpd: 21
> 15685 ? S 0:00 \_ ftpd: sa
> 16160 ? S 0:00 \_ ftpd: at
> 18482 ? S 0:00 \_ ftpd: 21
> .
> .
> .
> === Cut ===
>
Yes. This was previously reported by myself. Basically, what the
daemons are doing is:
int main (int argc, *argv[])
{ /* setproctitle() */
strcpy(argv[0], "New Name to be seen by `ps`");
This is NotGood(tm) because no child knows how much space was
available for the string. However, it's been done for ages. New
/proc/###/cmdline code (where `ps` gets the command-line), now
only allows you to read the length of the initial allocation.
The `fix` is not a kernel fix. Any child of a parent which desires
to overwrite argv[0], has to make sure the parent has enough space
allocated. This means that the child should be kicked-off with
its own arguments, with enough space allocated like:
parent's main(int args, char *argv[])
{
extract_command_line_pars(args, argv); /* Do first */
argv[0] = buffer0[0x100]; /* Replace pointers */
argv[1] = buffer1[0x100];
argv[2] = NULL;
switch(fork())
{
case 0: /* child */
strncpy(argv[0], "New stuff", 0x100);
If you fix all the `parent` daemons, you will have a good `ps` output.
Here is an example, program `status` before/after.
PID Name Stat CPU Mem Exe Command line
1 (init) S 0.02 220 188 init [5]
2 (kswapd) S 0.00 220 188
3 (kflushd) S 0.00 220 188
4 (kupdate) S 0.00 220 188
40 (crond) S 0.04 844 0 /usr/sbin/crond
59 (klogd) 0.02 796 20 /usr/sbin/klogd -s -k /System.ma
[Snipped...]
15241 (status) R 0.00 712 4 really big command
^^^^^^^^^^^^^^^^ Truncated
15625 (pine) S 0.14 2688 0 pine
15754 (status) R 0.01 712 4 really big command
line that _has_a_lot_of_stuff_in_it
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Fixed.
Cheers,
Dick Johnson
Penguin : Linux version 2.3.39 on an i686 machine (800.63 BogoMips).
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