[PATCH 4.9 12/33] openvswitch: Dont swap table in nlattr_set() after OVS_ATTR_NESTED is found

Greg Kroah-Hartman
2018-05-18T08:15:51Z

From: Stefano Brivio <sbrivio@redhat.com>

[ Upstream commit 72f17baf2352ded6a1d3f4bb2d15da8c678cd2cb ]

If an OVS_ATTR_NESTED attribute type is found while walking
through netlink attributes, we call nlattr_set() recursively
passing the length table for the following nested attributes, if
different from the current one.

However, once we're done with those sub-nested attributes, we
should continue walking through attributes using the current
table, instead of using the one related to the sub-nested
attributes.

For example, given this sequence:

1 OVS_KEY_ATTR_PRIORITY
2 OVS_KEY_ATTR_TUNNEL
3 OVS_TUNNEL_KEY_ATTR_ID
4 OVS_TUNNEL_KEY_ATTR_IPV4_SRC
5 OVS_TUNNEL_KEY_ATTR_IPV4_DST
6 OVS_TUNNEL_KEY_ATTR_TTL
7 OVS_TUNNEL_KEY_ATTR_TP_SRC
8 OVS_TUNNEL_KEY_ATTR_TP_DST
9 OVS_KEY_ATTR_IN_PORT
10 OVS_KEY_ATTR_SKB_MARK
11 OVS_KEY_ATTR_MPLS

we switch to the 'ovs_tunnel_key_lens' table on attribute #3,
and we don't switch back to 'ovs_key_lens' while setting
attributes #9 to #11 in the sequence. As OVS_KEY_ATTR_MPLS
evaluates to 21, and the array size of 'ovs_tunnel_key_lens' is
15, we also get this kind of KASan splat while accessing the
wrong table:

[ 7654.586496] ==================================================================
[ 7654.594573] BUG: KASAN: global-out-of-bounds in nlattr_set+0x164/0xde9 [openvswitch]
[ 7654.603214] Read of size 4 at addr ffffffffc169ecf0 by task handler29/87430
[ 7654.610983]
[ 7654.612644] CPU: 21 PID: 87430 Comm: handler29 Kdump: loaded Not tainted 3.10.0-866.el7.test.x86_64 #1
[ 7654.623030] Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
[ 7654.631379] Call Trace:
[ 7654.634108] [<ffffffffb65a7c50>] dump_stack+0x19/0x1b
[ 7654.639843] [<ffffffffb53ff373>] print_address_description+0x33/0x290
[ 7654.647129] [<ffffffffc169b37b>] ? nlattr_set+0x164/0xde9 [openvswitch]
[ 7654.654607] [<ffffffffb53ff812>] kasan_report.part.3+0x242/0x330
[ 7654.661406] [<ffffffffb53ff9b4>] __asan_report_load4_noabort+0x34/0x40
[ 7654.668789] [<ffffffffc169b37b>] nlattr_set+0x164/0xde9 [openvswitch]
[ 7654.676076] [<ffffffffc167ef68>] ovs_nla_get_match+0x10c8/0x1900 [openvswitch]
[ 7654.684234] [<ffffffffb61e9cc8>] ? genl_rcv+0x28/0x40
[ 7654.689968] [<ffffffffb61e7733>] ? netlink_unicast+0x3f3/0x590
[ 7654.696574] [<ffffffffc167dea0>] ? ovs_nla_put_tunnel_info+0xb0/0xb0 [openvswitch]
[ 7654.705122] [<ffffffffb4f41b50>] ? unwind_get_return_address+0xb0/0xb0
[ 7654.712503] [<ffffffffb65d9355>] ? system_call_fastpath+0x1c/0x21
[ 7654.719401] [<ffffffffb4f41d79>] ? update_stack_state+0x229/0x370
[ 7654.726298] [<ffffffffb4f41d79>] ? update_stack_state+0x229/0x370
[ 7654.733195] [<ffffffffb53fe4b5>] ? kasan_unpoison_shadow+0x35/0x50
[ 7654.740187] [<ffffffffb53fe62a>] ? kasan_kmalloc+0xaa/0xe0
[ 7654.746406] [<ffffffffb53fec32>] ? kasan_slab_alloc+0x12/0x20
[ 7654.752914] [<ffffffffb53fe711>] ? memset+0x31/0x40
[ 7654.758456] [<ffffffffc165bf92>] ovs_flow_cmd_new+0x2b2/0xf00 [openvswitch]

[snip]

[ 7655.132484] The buggy address belongs to the variable:
[ 7655.138226] ovs_tunnel_key_lens+0xf0/0xffffffffffffd400 [openvswitch]
[ 7655.145507]
[ 7655.147166] Memory state around the buggy address:
[ 7655.152514] ffffffffc169eb80: 00 00 00 00 00 00 00 00 00 00 fa fa fa fa fa fa
[ 7655.160585] ffffffffc169ec00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 7655.168644] >ffffffffc169ec80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa fa
[ 7655.176701] ^
[ 7655.184372] ffffffffc169ed00: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 05
[ 7655.192431] ffffffffc169ed80: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
[ 7655.200490] ==================================================================

Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Fixes: 982b52700482 ("openvswitch: Fix mask generation for nested attributes.")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/openvswitch/flow_netlink.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -1296,13 +1296,10 @@ static void nlattr_set(struct nlattr *at

/* The nlattr stream should already have been validated */
nla_for_each_nested(nla, attr, rem) {
- if (tbl[nla_type(nla)].len == OVS_ATTR_NESTED) {
- if (tbl[nla_type(nla)].next)
- tbl = tbl[nla_type(nla)].next;
- nlattr_set(nla, val, tbl);
- } else {
+ if (tbl[nla_type(nla)].len == OVS_ATTR_NESTED)
+ nlattr_set(nla, val, tbl[nla_type(nla)].next ? : tbl);
+ else
memset(nla_data(nla), val, nla_len(nla));
- }

if (nla_type(nla) == OVS_KEY_ATTR_CT_STATE)
*(u32 *)nla_data(nla) &= CT_SUPPORTED_MASK;