On Tue, Apr 10, 2012 at 3:00 PM, Andrew Morton
[off-list ref] wrote:

On Mon, 9 Apr 2012 14:59:00 -0500
Will Drewry [off-list ref] wrote:

quoted

quoted

quoted

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).

--
To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html