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Commit 6405f7f4 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus 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);

	}



	/*