mpls_label_ok() validates that the 'platform_label' array index from a userspace netlink message payload is valid. Under speculation the mpls_label_ok() result may not resolve in the CPU pipeline until after the index is used to access an array element. Sanitize the index to zero to prevent userspace-controlled arbitrary out-of-bounds speculation, a precursor for a speculative execution side channel vulnerability.

Cc: stable@vger.kernel.org Cc: "David S. Miller" davem@davemloft.net Cc: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- net/mpls/af_mpls.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index 8ca9915befc8..aae3565c3a92 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -8,6 +8,7 @@ #include <linux/ipv6.h> #include <linux/mpls.h> #include <linux/netconf.h> +#include <linux/nospec.h> #include <linux/vmalloc.h> #include <linux/percpu.h> #include <net/ip.h> @@ -935,24 +936,27 @@ static int mpls_nh_build_multi(struct mpls_route_config *cfg, return err; }

-static bool mpls_label_ok(struct net *net, unsigned int index, +static bool mpls_label_ok(struct net *net, unsigned int *index, struct netlink_ext_ack *extack) { + bool is_ok = true; + /* Reserved labels may not be set */ - if (index < MPLS_LABEL_FIRST_UNRESERVED) { + if (*index < MPLS_LABEL_FIRST_UNRESERVED) { NL_SET_ERR_MSG(extack, "Invalid label - must be MPLS_LABEL_FIRST_UNRESERVED or higher"); - return false; + is_ok = false; }

/* The full 20 bit range may not be supported. */ - if (index >= net->mpls.platform_labels) { + if (is_ok && *index >= net->mpls.platform_labels) { NL_SET_ERR_MSG(extack, "Label >= configured maximum in platform_labels"); - return false; + is_ok = false; }

- return true; + *index = array_index_nospec(*index, net->mpls.platform_labels); + return is_ok; }

static int mpls_route_add(struct mpls_route_config *cfg, @@ -975,7 +979,7 @@ static int mpls_route_add(struct mpls_route_config *cfg, index = find_free_label(net); }

- if (!mpls_label_ok(net, index, extack)) + if (!mpls_label_ok(net, &index, extack)) goto errout;

/* Append makes no sense with mpls */ @@ -1052,7 +1056,7 @@ static int mpls_route_del(struct mpls_route_config *cfg,

index = cfg->rc_label;

- if (!mpls_label_ok(net, index, extack)) + if (!mpls_label_ok(net, &index, extack)) goto errout;

mpls_route_update(net, index, NULL, &cfg->rc_nlinfo); @@ -1810,7 +1814,7 @@ static int rtm_to_route_config(struct sk_buff *skb, goto errout;

if (!mpls_label_ok(cfg->rc_nlinfo.nl_net, - cfg->rc_label, extack)) + &cfg->rc_label, extack)) goto errout; break; } @@ -2137,7 +2141,7 @@ static int mpls_getroute(struct sk_buff *in_skb, struct nlmsghdr *in_nlh, goto errout; }

- if (!mpls_label_ok(net, in_label, extack)) { + if (!mpls_label_ok(net, &in_label, extack)) { err = -EINVAL; goto errout; }