Re: [PATCH 1/2] exec: Make do_coredump more robust and safer when using pipes in core_pattern: recursive dump detection

Oleg Nesterov
2009-06-26T20:14:12Z

On 06/26, Neil Horman wrote:
>
> + if (core_limit == 0) {
> + /*
> + * Normally core limits are irrelevant to pipes, since
> + * we're not writing to the file system, but we use
> + * core_limit of 0 here as a speacial value. Any
> + * non-zero limit gets set to RLIM_INFINITY below, but
> + * a limit of 0 skips the dump. This is a consistent
> + * way to catch recursive crashes. We can still crash
> + * if the core_pattern binary sets RLIM_CORE = !0
> + * but it runs as root, and can do lots of stupid things
> + * Note that we use task_tgid_vnr here to grab the pid of the
> + * process group leader. That way we get the right pid if a thread
> + * in a multi-threaded core_pattern process dies.
> + */
> + printk(KERN_WARNING "Process %d(%s) has RLIMIT_CORE set to 0\n",
> + task_tgid_vnr(current), current->comm);
> + printk(KERN_WARNING "Aborting core\n");

Andrew has already pointed out this, unprivileged-user-triggerable
printk.

Doesn't look good, if core_pattern starts with "|" any user can set
RLIMIT_CORE = 0 and then just do

for (;;)
if (pid = fork())
kill(pid, SIGQUIT);

to DOS printk/syslog, no?

Oleg.