Messages in this thread Patch in this message | | | Date | Thu, 22 Nov 2007 19:14:59 +0300 | From | Oleg Nesterov <> | Subject | [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach |
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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>
--- PT/kernel/signal.c~1_ptrace_stop 2007-11-21 21:41:02.000000000 +0300 +++ PT/kernel/signal.c 2007-11-22 16:59:35.000000000 +0300 @@ -1628,11 +1628,11 @@ static void ptrace_stop(int exit_code, i } 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); } /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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