ip6mr: Fix potential Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Tue, 11 Dec 2018 20:10:08 +0000 (14:10 -0600)
committerDavid S. Miller <davem@davemloft.net>
Fri, 14 Dec 2018 23:34:28 +0000 (15:34 -0800)
commit69d2c86766da2ded2b70281f1bf242cb0d58a778
tree2dff5a7d1cb78ea10ed065a738fa4ba991ec3eac
parent51367e423c6501a26e67d91a655d2bc892303462
ip6mr: Fix potential Spectre v1 vulnerability

vr.mifi 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/ipv6/ip6mr.c:1845 ip6mr_ioctl() warn: potential spectre issue 'mrt->vif_table' [r] (local cap)
net/ipv6/ip6mr.c:1919 ip6mr_compat_ioctl() warn: potential spectre issue 'mrt->vif_table' [r] (local cap)

Fix this by sanitizing vr.mifi before using it to index mrt->vif_table'

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>
net/ipv6/ip6mr.c