From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 1 Dec 2010 20:46:24 +0000 (+0000)
Subject: filter: add a security check at install time
X-Git-Tag: v2.6.38-rc1~476^2~306
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2d5311e4e8272fd398fc1cf278f12fd6dee4074b;p=pandora-kernel.git

filter: add a security check at install time

We added some security checks in commit 57fe93b374a6
(filter: make sure filters dont read uninitialized memory) to close a
potential leak of kernel information to user.

This added a potential extra cost at run time, while we can perform a
check of the filter itself, to make sure a malicious user doesnt try to
abuse us.

This patch adds a check_loads() function, whole unique purpose is to
make this check, allocating a temporary array of mask. We scan the
filter and propagate a bitmask information, telling us if a load M(K) is
allowed because a previous store M(K) is guaranteed. (So that
sk_run_filter() can possibly not read unitialized memory)

Note: this can uncover application bug, denying a filter attach,
previously allowed.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Changli Gao <xiaosuo@gmail.com>
Acked-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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