Messages in this thread Patch in this message | | | Date | Tue, 11 Dec 2018 14:10:08 -0600 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] ip6mr: Fix potential Spectre v1 vulnerability |
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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> --- net/ipv6/ip6mr.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c index 8c63494400c4..5562cd7f6f56 100644 --- a/net/ipv6/ip6mr.c +++ b/net/ipv6/ip6mr.c @@ -52,6 +52,8 @@ #include <net/ip6_checksum.h> #include <linux/netconf.h> +#include <linux/nospec.h> + struct ip6mr_rule { struct fib_rule common; }; @@ -1841,6 +1843,7 @@ int ip6mr_ioctl(struct sock *sk, int cmd, void __user *arg) return -EFAULT; if (vr.mifi >= mrt->maxvif) return -EINVAL; + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif); read_lock(&mrt_lock); vif = &mrt->vif_table[vr.mifi]; if (VIF_EXISTS(mrt, vr.mifi)) { @@ -1915,6 +1918,7 @@ int ip6mr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg) return -EFAULT; if (vr.mifi >= mrt->maxvif) return -EINVAL; + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif); read_lock(&mrt_lock); vif = &mrt->vif_table[vr.mifi]; if (VIF_EXISTS(mrt, vr.mifi)) { -- 2.17.1
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