Commit ceca3c19 authored Apr 26, 2011 by Oleg Nesterov Committed by Chris Metcalf May 04, 2011

tile: do_hardwall_trap: do not play with task->sighand



1. do_hardwall_trap() checks ->sighand != NULL and then takes ->siglock.

   This is unsafe even if the task can't run (I assume it is pinned to
   the same CPU), its parent can reap the task and set ->sighand = NULL
   right after this check. Even if the compiler dosn't read ->sighand
   twice and this memory can't to away __group_send_sig_info() is wrong
   after that. Use do_send_sig_info().

2. Send SIGILL to the thread, not to the whole process. Unless it has
   the handler or blocked this kills the whole thread-group as before.
   IIUC, different threads can be bound to different rect's.

3. Check PF_EXITING instead of ->sighand. A zombie thread can go away
   but its ->sighand can be !NULL.

Reported-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

parent dc0b124d

arch/tile/kernel/hardwall.c

+2 −4

Original line number	Original line	Diff line number	Diff line
	@@ -268,12 +268,10 @@ void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
	found_processes = 0;		found_processes = 0;
	list_for_each_entry(p, &rect->task_head, thread.hardwall_list) {		list_for_each_entry(p, &rect->task_head, thread.hardwall_list) {
	BUG_ON(p->thread.hardwall != rect);		BUG_ON(p->thread.hardwall != rect);
	if (p->sighand) {		if (!(p->flags & PF_EXITING)) {
	found_processes = 1;		found_processes = 1;
	pr_notice("hardwall: killing %d\n", p->pid);		pr_notice("hardwall: killing %d\n", p->pid);
	spin_lock(&p->sighand->siglock);		do_send_sig_info(info.si_signo, &info, p, false);
	__group_send_sig_info(info.si_signo, &info, p);
	spin_unlock(&p->sighand->siglock);
	}		}
	}		}
	if (!found_processes)		if (!found_processes)