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    SubjectRe: [PATCH v17 08/15] seccomp: add system call filtering using BPF
    On Tue, Apr 10, 2012 at 3:00 PM, Andrew Morton
    <> wrote:
    > On Mon, 9 Apr 2012 14:59:00 -0500
    > Will Drewry <> wrote:
    >> >> I think this gives userspace an easy way of causing page allocation
    >> >> failure warnings, by permitting large kmalloc() attempts. __Add
    >> >> __GFP_NOWARN?
    >> >
    >> > Max is 32kb. sk_attach_filter() in net/core/filter.c is worse,
    >> > it allocates up to 512kb before even checking the length.
    >> >
    >> > What about using GFP_USER (and adding __GFP_NOWARN to GFP_USER) instead?
    >> It looks like GFP_USER|__GFP_NOWARN would make sense here.  I'll change it.
    > I'm not really sure why GFP_USER exists.  It's very rarely used, and
    > most usages are probably inappropriate.  To me it means "same as
    > GFP_HIGHUSER, only don't use highmem".  That's relevant to blockdev
    > pagecache and nothing else as far as I can tell.  And good luck working
    > out what the __GFP_HARDWALL does ;)

    I was wildly speculating about it, but maybe I should stop doing that.

    > This is a regular old allocation of kernel memory - the thing to use
    > here is GFP_KERNEL|__GFP_NOWARN.

    Sounds good - I've just changed the patchset to that effect.

    > (I'm surprised that we didn't remove __GFP_NOWARN ages ago - warning by
    > default is pretty obnoxious.  But the warning continues to be
    > occasionally useful and false positives are rare).
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      Last update: 2012-04-10 22:19    [W:0.022 / U:12.016 seconds]
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