Messages in this thread | | | Subject | Re: A better interface, perhaps: a timed signal flag | From | Steven Rostedt <> | Date | Fri, 28 Jul 2006 11:05:16 -0400 |
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On Fri, 2006-07-28 at 10:52 -0400, Theodore Tso wrote:
> Good point, and limiting this facility to one such timeout per > task_struct seems like a reasonable restriction. The downsides I can > see about about mapping the tasks' own task struct would be (a) a > potential security leak either now or in the future if some field in > the task_struct shouldn't be visible to a non-privileged userspace > program, and (b) exposing the task_struct might cause some (stupid) > programs to depend on the task_struct layout. Allocating an otherwise > empty 4k page just for this purpose wouldn't be all that horrible, > though, and would avoid these potential problems.
Actually, if you are going to map a page, then allow the user to do PAGE_SIZE / sizeof(*flag) timers. That way the user gets a single page mapped for this purpose, and can have multiple flags.
I would only limit it to one page though. Since this page can not be swapped out, if you allow for more than one page, a non privileged user can map in a bunch of non swappable pages and might be able to perform a DoS attack.
-- Steve
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