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    Subject[PATCH 4.14 004/101] ip6mr: Fix potential Spectre v1 vulnerability
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>

    [ Upstream commit 69d2c86766da2ded2b70281f1bf242cb0d58a778 ]

    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>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv6/ip6mr.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/net/ipv6/ip6mr.c
    +++ b/net/ipv6/ip6mr.c
    @@ -72,6 +72,8 @@ struct mr6_table {
    #endif
    };

    +#include <linux/nospec.h>
    +
    struct ip6mr_rule {
    struct fib_rule common;
    };
    @@ -1883,6 +1885,7 @@ int ip6mr_ioctl(struct sock *sk, int cmd
    return -EFAULT;
    if (vr.mifi >= mrt->maxvif)
    return -EINVAL;
    + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif);
    read_lock(&mrt_lock);
    vif = &mrt->vif6_table[vr.mifi];
    if (MIF_EXISTS(mrt, vr.mifi)) {
    @@ -1957,6 +1960,7 @@ int ip6mr_compat_ioctl(struct sock *sk,
    return -EFAULT;
    if (vr.mifi >= mrt->maxvif)
    return -EINVAL;
    + vr.mifi = array_index_nospec(vr.mifi, mrt->maxvif);
    read_lock(&mrt_lock);
    vif = &mrt->vif6_table[vr.mifi];
    if (MIF_EXISTS(mrt, vr.mifi)) {

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