ipv4: Fix potential Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Mon, 10 Dec 2018 18:41:24 +0000 (12:41 -0600)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 9 Jan 2019 16:38:31 +0000 (17:38 +0100)
commit360fb1db92dfe28145a12f48e6eefec2bf108a3a
tree27cad73bf197e18e0b5f9b815c9150789c3542dd
parent32403fd3b529a6e226f41314aa901a192be19af1
ipv4: Fix potential Spectre v1 vulnerability

[ Upstream commit 5648451e30a0d13d11796574919a359025d52cce ]

vr.vifi 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/ipv4/ipmr.c:1616 ipmr_ioctl() warn: potential spectre issue 'mrt->vif_table' [r] (local cap)
net/ipv4/ipmr.c:1690 ipmr_compat_ioctl() warn: potential spectre issue 'mrt->vif_table' [r] (local cap)

Fix this by sanitizing vr.vifi 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/ipv4/ipmr.c