4.9-stable review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
[ 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 | 3 +++ 1 file changed, 3 insertions(+)
--- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -68,6 +68,8 @@ #include <linux/netconf.h> #include <net/nexthop.h>
+#include <linux/nospec.h> + struct ipmr_rule { struct fib_rule common; }; @@ -1562,6 +1564,7 @@ int ipmr_compat_ioctl(struct sock *sk, u 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)) {