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ptrace_stop: fix the race with ptrace detach+attach 

If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops
tasklist and then changes the ->state from TASK_TRACED to TASK_RUNNING.

This can fool another tracer which attaches to us in between.  Change the
->state under tasklist_lock to ensure that ptrace_check_attach() can't wrongly
succeed.  Also, remove the unnecessary mb().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2008-02-08 04:19:00 -08:00 committed by Linus Torvalds
parent c0c0b649d6
commit 6405f7f467
1 changed files with 3 additions and 3 deletions
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6
kernel/signal.c
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@ -1638,11 +1638,11 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
} else {
/*
* By the time we got the lock, our tracer went away.
* Don't stop here.
* Don't drop the lock yet, another tracer may come.
*/
read_unlock(&tasklist_lock);
set_current_state(TASK_RUNNING);
__set_current_state(TASK_RUNNING);
current->exit_code = nostop_code;
read_unlock(&tasklist_lock);
}
/*