Re: [PATCH] Reserve N process to root

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Gustavo Chain wrote:
I think it's necessary to reserve some pids to the super user.
5 must be sufficient.

Why?  (Sorry if I missed something.)

Shouldn't you test for error return before the pid is allocated? Otherwise, I think, you have to free it. Thus:
 long do_fork(unsigned long clone_flags,
              int __user *parent_tidptr,
              int __user *child_tidptr)
 {
+#define RESERVED_PIDS   5      /* danged if I know why */
+
+       if (!capable(CAP_SYS_ADMIN) && nr_threads >= max_threads - RESERVED_PIDS)
+               return -EAGAIN;
+

        struct task_struct *p;
        int trace = 0;
        struct pid *pid = alloc_pid();
        long nr;
if (!pid)
                return -EAGAIN;
        nr = pid->nr;

(While I'm being picky, I don't like braces around a simple return, and neither, I note, does the style guide.)
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