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

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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>
This commit is contained in:
Oleg Nesterov 2011-04-26 22:37:11 +02:00 committed by Chris Metcalf
parent dc0b124d8e
commit ceca3c193e
1 changed files with 2 additions and 4 deletions
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6
arch/tile/kernel/hardwall.c
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@ -268,12 +268,10 @@ void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
found_processes = 0;
list_for_each_entry(p, &rect->task_head, thread.hardwall_list) {
BUG_ON(p->thread.hardwall != rect);
if (p->sighand) {
if (!(p->flags & PF_EXITING)) {
found_processes = 1;
pr_notice("hardwall: killing %d\n", p->pid);
spin_lock(&p->sighand->siglock);
__group_send_sig_info(info.si_signo, &info, p);
spin_unlock(&p->sighand->siglock);
do_send_sig_info(info.si_signo, &info, p, false);
}
}
if (!found_processes)