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ptrace, x86: fix the usage of ptrace_fork()

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I noticed by pure accident we have ptrace_fork() and friends. This was
added by "x86, bts: add fork and exit handling", commit
bf53de907dfdaac178c92d774aae7370d7b97d20.

I can't test this, ds_request_bts() returns -EOPNOTSUPP, but I strongly
believe this needs the fix. I think something like this program

	int main(void)
	{
		int pid = fork();

		if (!pid) {
			ptrace(PTRACE_TRACEME, 0, NULL, NULL);
			kill(getpid(), SIGSTOP);
			fork();
		} else {
			struct ptrace_bts_config bts = {
				.flags = PTRACE_BTS_O_ALLOC,
				.size  = 4 * 4096,
			};

			wait(NULL);

			ptrace(PTRACE_SETOPTIONS, pid, NULL, PTRACE_O_TRACEFORK);
			ptrace(PTRACE_BTS_CONFIG, pid, &bts, sizeof(bts));
			ptrace(PTRACE_CONT, pid, NULL, NULL);

			sleep(1);
		}

		return 0;
	}

should crash the kernel.

If the task is traced by its natural parent ptrace_reparented() returns 0
but we should clear ->btsxxx anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Oleg Nesterov 2009-02-09 02:02:33 +01:00 committed by Ingo Molnar
parent b52af40923
commit 06eb23b1ba
1 changed files with 1 additions and 1 deletions
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2
kernel/fork.c
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@ -1093,7 +1093,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
#ifdef CONFIG_DEBUG_MUTEXES
p->blocked_on = NULL; /* not blocked yet */
#endif
if (unlikely(ptrace_reparented(current)))
if (unlikely(current->ptrace))
ptrace_fork(p, clone_flags);
/* Perform scheduler related setup. Assign this task to a CPU. */