Commit a893a84e authored Jun 23, 2009 by Oleg Nesterov Committed by James Morris Jun 25, 2009

mm_for_maps: simplify, use ptrace_may_access()



It would be nice to kill __ptrace_may_access(). It requires task_lock(),
but this lock is only needed to read mm->flags in the middle.

Convert mm_for_maps() to use ptrace_may_access(), this also simplifies
the code a little bit.

Also, we do not need to take ->mmap_sem in advance. In fact I think
mm_for_maps() should not play with ->mmap_sem at all, the caller should
take this lock.

With or without this patch, without ->cred_guard_mutex held we can race
with exec() and get the new ->mm but check old creds.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

parent 9e48858f

fs/proc/base.c

+11 −12

Original line number	Diff line number	Diff line
		@@ -237,21 +237,20 @@ struct mm_struct mm_for_maps(struct task_struct task)
		struct mm_struct *mm = get_task_mm(task);
		if (!mm)
		return NULL;
		down_read(&mm->mmap_sem);
		task_lock(task);
		if (task->mm != mm)
		goto out;
		if (task->mm != current->mm &&
		__ptrace_may_access(task, PTRACE_MODE_READ) < 0)
		goto out;
		task_unlock(task);
		return mm;
		out:
		task_unlock(task);
		up_read(&mm->mmap_sem);
		if (mm != current->mm) {
		/*
		* task->mm can be changed before security check,
		* in that case we must notice the change after.
		*/
		if (!ptrace_may_access(task, PTRACE_MODE_READ) \|\|
		mm != task->mm) {
		mmput(mm);
		return NULL;
		}
		}
		down_read(&mm->mmap_sem);
		return mm;
		}

		static int proc_pid_cmdline(struct task_struct task, char buffer)
		{