4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[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@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/mpls/af_mpls.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
--- 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>
@@ -756,17 +757,20 @@ 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)
@@ -787,7 +791,7 @@ static int mpls_route_add(struct mpls_ro
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 */
@@ -848,7 +852,7 @@ static int mpls_route_del(struct mpls_ro
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);
@@ -1283,7 +1287,7 @@ static int rtm_to_route_config(struct sk
goto errout;
if (!mpls_label_ok(cfg->rc_nlinfo.nl_net,
- cfg->rc_label))
+ &cfg->rc_label))
goto errout;
break;
}