On Fri, 21 Jan 2000, Richard B. Johnson wrote:
Thank you for your reply. Now I do have an overall idea how to get sendmail,
inetd and several another apps fixed.
> 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).
>
===========================================================================
Sergey Kubushin aka the Tamer < > The impossible we do immediately.
e-mail: ksi@ksi-linux.com SK320-RIPE < > Miracles require 24-hour notice.
===========================================================================
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