Commit 6405f7f4 authored Feb 08, 2008 by Oleg Nesterov Committed by Linus Torvalds Feb 08, 2008

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>

parent c0c0b649

kernel/signal.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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);
		}

		/*

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