From 5648451e30a0d13d11796574919a359025d52cce Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 10 Dec 2018 12:41:24 -0600 Subject: [PATCH] ipv4: Fix potential Spectre v1 vulnerability 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 Signed-off-by: David S. Miller --- net/ipv4/ipmr.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index a6defbec4f1b..e7a3879cedd0 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -69,6 +69,8 @@ #include #include +#include + struct ipmr_rule { struct fib_rule common; }; @@ -1612,6 +1614,7 @@ int ipmr_ioctl(struct sock *sk, int cmd, void __user *arg) return -EFAULT; if (vr.vifi >= mrt->maxvif) return -EINVAL; + vr.vifi = array_index_nospec(vr.vifi, mrt->maxvif); read_lock(&mrt_lock); vif = &mrt->vif_table[vr.vifi]; if (VIF_EXISTS(mrt, vr.vifi)) { @@ -1686,6 +1689,7 @@ int ipmr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg) return -EFAULT; if (vr.vifi >= mrt->maxvif) return -EINVAL; + vr.vifi = array_index_nospec(vr.vifi, mrt->maxvif); read_lock(&mrt_lock); vif = &mrt->vif_table[vr.vifi]; if (VIF_EXISTS(mrt, vr.vifi)) {