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can: af_can: Fix Spectre v1 vulnerability

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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/can/af_can.c:115 can_get_proto() warn: potential spectre issue 'proto_tab' [w]

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>
This commit is contained in:
Gustavo A. R. Silva 2018-12-21 15:22:29 -06:00 committed by David S. Miller
parent 6b8d95f179
commit a3ac5817ff
1 changed files with 2 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
net/can/af_can.c
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@ -59,6 +59,7 @@
#include <linux/can/core.h> #include <linux/can/core.h>
#include <linux/can/skb.h> #include <linux/can/skb.h>
#include <linux/ratelimit.h> #include <linux/ratelimit.h>
#include <linux/nospec.h>
#include <net/net_namespace.h> #include <net/net_namespace.h>
#include <net/sock.h> #include <net/sock.h>
@ -136,6 +137,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
if (protocol < 0 || protocol >= CAN_NPROTO) if (protocol < 0 || protocol >= CAN_NPROTO)
return -EINVAL; return -EINVAL;
protocol = array_index_nospec(protocol, CAN_NPROTO);
cp = can_get_proto(protocol); cp = can_get_proto(protocol);