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
Unified · Split
| @@ -52,6 +52,8 @@ · 51 unmodified lines | ||
| 52 | 52 | #include <net/ip6_checksum.h> |
| 53 | 53 | #include <linux/netconf.h> |
| 54 | 54 | |
| 55 | +#include <linux/nospec.h> | |
| 56 | + | |
| 55 | 57 | struct ip6mr_rule { |
| 56 | 58 | struct fib_rule common; |
| 57 | 59 | }; |
| @@ -1841,6 +1843,7 @@ int ip6mr_ioctl(struct sock *sk, int cmd, void __user *arg) · 1783 unmodified lines | ||
| 1841 | 1843 | return -EFAULT; |
| 1842 | 1844 | if (vr.mifi >= mrt->maxvif) |
| 1843 | 1845 | return -EINVAL; |
| 1846 | + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif); | |
| 1844 | 1847 | read_lock(&mrt_lock); |
| 1845 | 1848 | vif = &mrt->vif_table[vr.mifi]; |
| 1846 | 1849 | if (VIF_EXISTS(mrt, vr.mifi)) { |
| @@ -1915,6 +1918,7 @@ int ip6mr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg) · 68 unmodified lines | ||
| 1915 | 1918 | return -EFAULT; |
| 1916 | 1919 | if (vr.mifi >= mrt->maxvif) |
| 1917 | 1920 | return -EINVAL; |
| 1921 | + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif); | |
| 1918 | 1922 | read_lock(&mrt_lock); |
| 1919 | 1923 | vif = &mrt->vif_table[vr.mifi]; |
| 1920 | 1924 | if (VIF_EXISTS(mrt, vr.mifi)) { |