Changes in fork ?

[Ed McCaul]

I do not know who  put me on this list but get me off of it now.










At 12:02 PM 1/23/00 +0000, Nick Holloway wrote:
>root en chaos.analogic.com (Richard B. Johnson) writes:
> > On Fri, 21 Jan 2000, Sergey Kubushin wrote:
> > > 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
> >
> > 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.
>
>Normally the implementations of setproctitle() are a little more careful
>than that.  They use the processes environment space in addition to the
>argument space.  This does rely on them being contiguous memory areas.
>
>Looking as binfmt_elf and binfmt_aout, this still appears to be true in
>2.3.40, so the previous behaviour can be restored by limiting the area
>returned in /proc/$$/cmdline to be env_end, instead of arg_end.
>
>Note that the contents returned in /proc/$$/environ are already trashed
>by code that uses setproctitle().
>
>--- /usr/src/linux-2.3/fs/proc/base.c   Sun Jan 23 10:50:53 2000
>+++ base.c      Sun Jan 23 11:45:03 2000
>@@ -120,7 +120,7 @@
>         struct mm_struct *mm = task->mm;
>         int res = 0;
>         if (mm) {
>-               int len = mm->arg_end - mm->arg_start;
>+               int len = mm->env_end - mm->arg_start;
>                 if (len > PAGE_SIZE)
>                         len = PAGE_SIZE;
>                 res = access_process_vm(task, mm->arg_start, buffer, len, 0);
>
>--
>  `O O'  | Nick.Holloway en alfie.demon.co.uk
>// ^ \\ | http://www.alfie.demon.co.uk/
>
>-
>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>the body of a message to majordomo en vger.rutgers.edu
>Please read the FAQ at http://www.tux.org/lkml/


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo en vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/