[lkml]   [2011]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [RFC v1] implement SL*B and stack usercopy runtime checks
    On Sun, Jul 03, 2011 at 11:27 -0700, Linus Torvalds wrote:
    > That patch is entirely insane. No way in hell will that ever get merged.

    Sure, this is just an RFC :) I didn't think about proposing it as a
    patch as is, I tried to just show how/what checks it introduces.

    > copy_to/from_user() is some of the most performance-critical code, and
    > runs a *lot*, often for fairly small structures (ie 'fstat()' etc).
    > Adding random ad-hoc tests to it is entirely inappropriate. Doing so
    > unconditionally is insane.

    That's why I've asked whether it makes sense to guard it with
    CONFIG_XXX, defaults to =n. Some distributions might think it makes
    sense to enable it sacrificing some speed.

    Will do.

    > If you seriously clean it up (that at a minimum includes things like
    > making it configurable using some pretty helper function that just
    > compiles away for all the normal cases,

    Hm, it is not as simple as it looks at the first glance - even if the
    object size is known at the compile time (__compiletime_object_size), it
    might be a field of a structure, which crosses the slab object
    boundaries because of an overflow.

    However, if interpret constants fed to copy_*_user() as equivalent to
    {get,put}_user() (== worry about size argument overflow only), then it
    might be useful here.

    > if (!slab_access_ok(to, n) || !stack_access_ok(to, n))

    OK :)


    Vasiliy Kulikov - bringing security into open computing environments

     \ /
      Last update: 2011-07-03 20:59    [W:0.021 / U:8.716 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site