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mpls, nospec: Sanitize array index in mpls_label_ok()

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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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dan Williams 2018-03-08 18:39:24 +00:00 • committed by Greg Kroah-Hartman
parent 4bd01ca763
commit e7f17d033e
1 changed files with 13 additions and 9 deletions
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22
net/mpls/af_mpls.c
View file

@ -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;
}