| Date | Thu, 02 Aug 2012 11:47:30 -0700 | From | Andy Lutomirski <> | Subject | Re: [PATCH 03/17] perf, x86: Add copy_from_user_nmi_nochk for best effort copy |
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On 07/22/2012 05:14 AM, Jiri Olsa wrote: > Adding copy_from_user_nmi_nochk that provides the best effort > copy regardless the requesting size crossing the task boundary. > > This is going to be useful for stack dump we need in post > DWARF CFI based unwind, where we have predefined size of > the user stack to dump, and we need to store the most of > the requested dump size, regardless this size is crossing > the task boundary.
Huh? This is a TASK_SIZE check, which makes sure that the request doesn't cross into kernel land. Otherwise userspace could presumably read kernel memory by setting bogus values of sp.
--Andy
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