On Fri, 2005-03-25 at 04:17 +1000, Triffid Hunter wrote:
> you can limit the max number of processes by putting the following into /etc/security/limits.conf (on my distro, and quite a number of others according to google too)
>
> * hard nproc <max # processes>
>
> you can also limit quite a number of other things in this file, and other files in that directory.
I bet your PAM nonaware daemons started at boot are not affected by
those settings. The point is that if you gain access through a non-root
daemon started from boot scripts, you are no longer limited
by /etc/security/limits.conf.
Try to set hard nproc limits for user UID and run this from your boot
script:
#define UID 65534
#define MAX 65535
int pids[MAX];
int main() {
int count = 0; pid_t pid;
if (setuid(UID) < 0) { perror("setuid"); exit(1); }
while ((pid = fork()) >= 0 && count < MAX) {
if (pid == 0) { sleep(300); exit(); }
pids[count++] = pid;
}
printf("Forked %i new processes\n", count);
while (count--) kill(pids[count], SIGTERM);
}
You will see that even if user UID is limited
in /etc/security/limits.conf it will be able to fork many more
processes.
> > It should exist a global limit in case someone could spawn
> > a shell without limits through some flawed application.
I agree on this one. Or the RLIMIT_NPROC should be set to a lower value
by default.
--
Natanael Copa
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