From: David S. Miller <davem@davemloft.net>
Date: Fri, 10 Oct 2014 19:37:36 +0000 (-0400)
Subject: Merge branch 'net-drivers-pgcnt'
X-Git-Tag: v4.9.8~5486^2~66
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=35b7a1915aa33da812074744647db0d9262a555c;p=platform%2Fkernel%2Flinux-rpi3.git

Merge branch 'net-drivers-pgcnt'

Eric Dumazet says:

====================
net: fix races accessing page->_count

This is illegal to use atomic_set(&page->_count, ...) even if we 'own'
the page. Other entities in the kernel need to use get_page_unless_zero()
to get a reference to the page before testing page properties, so we could
loose a refcount increment.

The only case it is valid is when page->_count is 0, we can use this in
__netdev_alloc_frag()

Note that I never seen crashes caused by these races, the issue was reported
by Andres Lagar-Cavilla and Hugh Dickins.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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35b7a1915aa33da812074744647db0d9262a555c