[lkml]   [2012]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [kernel-hardening] Re: Add overflow protection to kref
    On Fri, Feb 17, 2012 at 05:44:57PM -0800, Roland Dreier wrote:
    > On Fri, Feb 17, 2012 at 3:39 PM, Djalal Harouni <> wrote:
    > >> 2) what to do with architectures-loosers?
    > > There is lib/atomic64.c but with a static hashed array of raw_spinlocks.
    > Even leaving aside performance impact of atomic64_t (and probably
    > in most cases the performance of kref is not important at all), it is
    > unfortunate to bloat the size from 4 bytes to 8 bytes.
    > It seems much better to have some out-of-line code for overflow
    > checking rather than increasing the size of every data structure
    > that embeds a kref.

    Please realize that kref is an in-line structure now.

    > Greg, I'm not sure why you're opposed to adding this checking...
    > it's pretty clear that buggy error paths that forget to do a put are
    > pretty common and will continue to be common in new code, and
    > making them harder to exploit seems pretty sane to me.
    > What's the downside?

    The downside is that there has not even been a patch sent for any of
    this. Combine that with a lack of understanding about reference
    counting and atomic_t usages in the kernel, and the whole thing is ripe
    for misunderstanding and confusion.

    greg k-h

     \ /
      Last update: 2012-02-18 17:27    [W:0.021 / U:19.000 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site