From: Dan Williams dan.j.williams@intel.com
commit 3968523f855050b8195134da951b87c20bd66130 upstream.
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: "David S. Miller" davem@davemloft.net Cc: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 4.4: - mpls_label_ok() doesn't take an extack parameter - Drop change in mpls_getroute()] Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk --- net/mpls/af_mpls.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index ff7f7f05523a..c2ce7dec5198 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -7,6 +7,7 @@ #include <linux/if_arp.h> #include <linux/ipv6.h> #include <linux/mpls.h> +#include <linux/nospec.h> #include <linux/vmalloc.h> #include <net/ip.h> #include <net/dst.h> @@ -714,17 +715,20 @@ errout: return err; }
-static bool mpls_label_ok(struct net *net, unsigned int index) +static bool mpls_label_ok(struct net *net, unsigned int *index) { + bool is_ok = true; + /* Reserved labels may not be set */ - if (index < MPLS_LABEL_FIRST_UNRESERVED) - return false; + if (*index < MPLS_LABEL_FIRST_UNRESERVED) + is_ok = false;
/* The full 20 bit range may not be supported. */ - if (index >= net->mpls.platform_labels) - return false; + if (is_ok && *index >= net->mpls.platform_labels) + 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) @@ -745,7 +749,7 @@ static int mpls_route_add(struct mpls_route_config *cfg) index = find_free_label(net); }
- if (!mpls_label_ok(net, index)) + if (!mpls_label_ok(net, &index)) goto errout;
/* Append makes no sense with mpls */ @@ -806,7 +810,7 @@ static int mpls_route_del(struct mpls_route_config *cfg)
index = cfg->rc_label;
- if (!mpls_label_ok(net, index)) + if (!mpls_label_ok(net, &index)) goto errout;
mpls_route_update(net, index, NULL, &cfg->rc_nlinfo); @@ -1166,7 +1170,7 @@ static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh, goto errout;
if (!mpls_label_ok(cfg->rc_nlinfo.nl_net, - cfg->rc_label)) + &cfg->rc_label)) goto errout; break; }