[PATCH linux-next] vpda: correctly size vdpa_nl_policy

[Eric Dumazet <eric.dumazet@gmail.com>]

From: Eric Dumazet <edumazet@google.com>

We need to ensure last entry of vdpa_nl_policy[]
is zero, otherwise out-of-bounds access is hurting us.

BUG: KASAN: global-out-of-bounds in netlink_policy_dump_add_policy+0x3b6/0x440   net/netlink/policy.c:160
Read of size 1 at addr ffffffff89cc61d0 by task syz-executor181/8413

CPU: 0 PID: 8413 Comm: syz-executor181 Not tainted 5.11.0-rc6-next-20210205-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack   lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163   lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5/0x2f8   mm/kasan/report.c:232
 __kasan_report   mm/kasan/report.c:399 [inline]
 kasan_report.cold+0x7c/0xd8   mm/kasan/report.c:416
 netlink_policy_dump_add_policy+0x3b6/0x440   net/netlink/policy.c:160
 ctrl_dumppolicy_start+0x3e1/0x760   net/netlink/genetlink.c:1181
 genl_start+0x3cc/0x670   net/netlink/genetlink.c:604
 __netlink_dump_start+0x584/0x900   net/netlink/af_netlink.c:2363
 genl_family_rcv_msg_dumpit+0x2af/0x310   net/netlink/genetlink.c:686
 genl_family_rcv_msg   net/netlink/genetlink.c:780 [inline]
 genl_rcv_msg+0x434/0x580   net/netlink/genetlink.c:800
 netlink_rcv_skb+0x153/0x420   net/netlink/af_netlink.c:2494
 genl_rcv+0x24/0x40   net/netlink/genetlink.c:811
 netlink_unicast_kernel   net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0   net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90   net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec   net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120   net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810   net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170   net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0   net/socket.c:2437
 do_syscall_64+0x2d/0x70   arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x43ef29
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc75c06108 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ef29
RDX: 0000000000000000 RSI: 00000000200029c0 RDI: 0000000000000003
RBP: 0000000000402f10 R08: 00000000004ac018 R09: 0000000000400488
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402fa0
R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488

The buggy address belongs to the variable:
 vdpa_nl_policy+0x90/0x3a00

Memory state around the buggy address:
 ffffffff89cc6080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff89cc6100: 00 00 00 00 f9 f9 f9 f9 00 00 00 00 00 00 00 00
>ffffffff89cc6180: 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9
                                                 ^
 ffffffff89cc6200: 05 f9 f9 f9 f9 f9 f9 f9 00 00 07 f9 f9 f9 f9 f9
 ffffffff89cc6280: 00 00 00 01 f9 f9 f9 f9 00 07 f9 f9 f9 f9 f9 f9

Fixes: be7f5be9e84a ("vdpa: Define vdpa mgmt device, ops and a netlink interface")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Parav Pandit <parav@nvidia.com>
Cc: Eli Cohen <elic@nvidia.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vdpa/vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 9700a0adcca089fe9abb0b211fada314fa4a04ef..3d997b3893452f4da6a6800e128c57a9a024c0ad 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -603,7 +603,7 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callba
 	return msg->len;
 }
 
-static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX] = {
+static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
 	[VDPA_ATTR_MGMTDEV_BUS_NAME] = { .type = NLA_NUL_STRING },
 	[VDPA_ATTR_MGMTDEV_DEV_NAME] = { .type = NLA_STRING },
 	[VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
-- 
2.30.0.478.g8a0d178c01-goog