From: Eric Dumazet <edumazet@google.com>
Date: Fri, 10 Oct 2014 11:48:18 +0000 (-0700)
Subject: net: fix races in page->_count manipulation
X-Git-Tag: fixes-against-v3.18-rc2~115^2~1^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4c450583d9d0a8241f0f62b80038ac47b43ff843;p=pandora-kernel.git

net: fix races in page->_count manipulation

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

Fixes: 540eb7bf0bbed ("net: Update alloc frag to reduce get/put page usage and recycle pages")
Signed-off-by: Eric Dumaze <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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