linux-kernel - Re: ptrace && cred_exec_mutex (Was: [PATCH] ptrace: tracehook_unsafe

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Date:	Sat, 25 Apr 2009 11:54:13 +0100
From:	David Howells <dhowells@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	dhowells@...hat.com, Roland McGrath <roland@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: ptrace && cred_exec_mutex (Was: [PATCH] ptrace: tracehook_unsafe_exec: remove the stale comment)

Oleg Nesterov <oleg@...hat.com> wrote:

> Yes. Except it looks like ->cred_exec_mutex is never used in fact.

I must to be missing something...  I see that:

	int ptrace_attach(struct task_struct *task)
	{
	...
		/* Protect exec's credential calculations against our interference;
		 * SUID, SGID and LSM creds get determined differently under ptrace.
		 */
		retval = mutex_lock_interruptible(&current->cred_exec_mutex);
	...
	}

And:

	int do_execve(...)
	{
	...
		retval = mutex_lock_interruptible(&current->cred_exec_mutex);
		if (retval < 0)
			goto out_free;
	...
	}

So how is it not used?

David
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