[PATCH] proc: optimize proc_check_dentry_visible
The code doesn't need to sleep to when making this check so I can just do the comparison and not worry about the reference counts. TODO: While looking at this I realized that my original cleanup did not push the permission check far enough down into the stack. The call of proc_check_dentry_visible needs to move out of the generic proc readlink/follow link code and into the individual get_link instances. Otherwise the shared resources checks are not quite correct (shared files_struct does not require a shared fs_struct), and there are races with unshare. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -1074,24 +1074,27 @@ static int proc_check_dentry_visible(struct inode *inode,
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* namespace, or are simply process local (like pipes).
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*/
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struct task_struct *task;
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struct files_struct *task_files, *files;
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int error = -EACCES;
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/* See if the the two tasks share a commone set of
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* file descriptors. If so everything is visible.
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*/
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task = get_proc_task(inode);
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if (!task)
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goto out;
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files = get_files_struct(current);
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task_files = get_files_struct(task);
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if (files && task_files && (files == task_files))
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error = 0;
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if (task_files)
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put_files_struct(task_files);
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if (files)
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put_files_struct(files);
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put_task_struct(task);
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rcu_read_lock();
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task = tref_task(proc_tref(inode));
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if (task) {
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struct files_struct *task_files, *files;
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/* This test answeres the question:
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* Is there a point in time since we looked up the
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* file descriptor where the two tasks share the
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* same files struct?
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*/
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rmb();
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files = current->files;
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task_files = task->files;
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if (files && (files == task_files))
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error = 0;
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}
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rcu_read_unlock();
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if (!error)
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goto out;
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