Commit 501f9328 authored Mar 21, 2020 by Bernd Edlinger Committed by Eric W. Biederman Mar 25, 2020

pidfd: Use new infrastructure to fix deadlocks in execve



This changes __pidfd_fget to use the new exec_update_mutex
instead of cred_guard_mutex.

This should be safe, as the credentials do not change
before exec_update_mutex is locked.  Therefore whatever
file access is possible with holding the cred_guard_mutex
here is also possbile with the exec_update_mutex.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

parent 69143038

kernel/pid.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -577,7 +577,7 @@ static struct file __pidfd_fget(struct task_struct task, int fd)
		struct file *file;
		int ret;

		ret = mutex_lock_killable(&task->signal->cred_guard_mutex);
		ret = mutex_lock_killable(&task->signal->exec_update_mutex);
		if (ret)
		return ERR_PTR(ret);

		@@ -586,7 +586,7 @@ static struct file __pidfd_fget(struct task_struct task, int fd)
		else
		file = ERR_PTR(-EPERM);

		mutex_unlock(&task->signal->cred_guard_mutex);
		mutex_unlock(&task->signal->exec_update_mutex);

		return file ?: ERR_PTR(-EBADF);
		}

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