Commit d686026b authored Dec 21, 2018 by Gustavo A. R. Silva Committed by David S. Miller Dec 22, 2018

phonet: af_phonet: Fix Spectre v1 vulnerability

protocol is indirectly controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

net/phonet/af_phonet.c:48 phonet_proto_get() warn: potential spectre issue 'proto_tab' [w] (local cap)

Fix this by sanitizing protocol before using it to index proto_tab.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2



Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 50d52586

net/phonet/af_phonet.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -34,6 +34,8 @@
		#include <net/phonet/phonet.h>
		#include <net/phonet/pn_dev.h>

		#include <linux/nospec.h>

		/* Transport protocol registration */
		static const struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;

		@@ -43,6 +45,7 @@ static const struct phonet_protocol *phonet_proto_get(unsigned int protocol)

		if (protocol >= PHONET_NPROTO)
		return NULL;
		protocol = array_index_nospec(protocol, PHONET_NPROTO);

		rcu_read_lock();
		pp = rcu_dereference(proto_tab[protocol]);

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