[PATCH 4.14 01/36] netfilter: nf_tables: fix NULL pointer dereference on nft_ct_helper_obj_dump()

From: Greg Kroah-Hartman
Date: Thu Jun 14 2018 - 10:37:41 EST

4.14-stable review patch. If anyone has any objections, please let me know.

------------------

From: Taehee Yoo <ap420073@xxxxxxxxx>

commit b71534583f22d08c3e3563bf5100aeb5f5c9fbe5 upstream.

In the nft_ct_helper_obj_dump(), always priv->helper4 is dereferenced.
But if family is ipv6, priv->helper6 should be dereferenced.

Steps to reproduces:

#test.nft
table ip6 filter {
ct helper ftp {
type "ftp" protocol tcp
}
chain input {
type filter hook input priority 4;
ct helper set "ftp"
}
}

%nft -f test.nft
%nft list ruleset

we can see the below messages:

[ 916.286233] kasan: GPF could be caused by NULL-ptr deref or user memory access
[ 916.294777] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 916.302613] Modules linked in: nft_objref nf_conntrack_sip nf_conntrack_snmp nf_conntrack_broadcast nf_conntrack_ftp nft_ct nf_conntrack nf_tables nfnetlink [last unloaded: nfnetlink]
[ 916.318758] CPU: 1 PID: 2093 Comm: nft Not tainted 4.17.0-rc4+ #181
[ 916.326772] Hardware name: To be filled by O.E.M. To be filled by O.E.M./Aptio CRB, BIOS 5.6.5 07/08/2015
[ 916.338773] RIP: 0010:strlen+0x1a/0x90
[ 916.342781] RSP: 0018:ffff88010ff0f2f8 EFLAGS: 00010292
[ 916.346773] RAX: dffffc0000000000 RBX: ffff880119b26ee8 RCX: ffff88010c150038
[ 916.354777] RDX: 0000000000000002 RSI: ffff880119b26ee8 RDI: 0000000000000010
[ 916.362773] RBP: 0000000000000010 R08: 0000000000007e88 R09: ffff88010c15003c
[ 916.370773] R10: ffff88010c150037 R11: ffffed002182a007 R12: ffff88010ff04040
[ 916.378779] R13: 0000000000000010 R14: ffff880119b26f30 R15: ffff88010ff04110
[ 916.387265] FS: 00007f57a1997700(0000) GS:ffff88011b800000(0000) knlGS:0000000000000000
[ 916.394785] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 916.402778] CR2: 00007f57a0ac80f0 CR3: 000000010ff02000 CR4: 00000000001006e0
[ 916.410772] Call Trace:
[ 916.414787] nft_ct_helper_obj_dump+0x94/0x200 [nft_ct]
[ 916.418779] ? nft_ct_set_eval+0x560/0x560 [nft_ct]
[ 916.426771] ? memset+0x1f/0x40
[ 916.426771] ? __nla_reserve+0x92/0xb0
[ 916.434774] ? memcpy+0x34/0x50
[ 916.434774] nf_tables_fill_obj_info+0x484/0x860 [nf_tables]
[ 916.442773] ? __nft_release_basechain+0x600/0x600 [nf_tables]
[ 916.450779] ? lock_acquire+0x193/0x380
[ 916.454771] ? lock_acquire+0x193/0x380
[ 916.458789] ? nf_tables_dump_obj+0x148/0xcb0 [nf_tables]
[ 916.462777] nf_tables_dump_obj+0x5f0/0xcb0 [nf_tables]
[ 916.470769] ? __alloc_skb+0x30b/0x500
[ 916.474779] netlink_dump+0x752/0xb50
[ 916.478775] __netlink_dump_start+0x4d3/0x750
[ 916.482784] nf_tables_getobj+0x27a/0x930 [nf_tables]
[ 916.490774] ? nft_obj_notify+0x100/0x100 [nf_tables]
[ 916.494772] ? nf_tables_getobj+0x930/0x930 [nf_tables]
[ 916.502579] ? nf_tables_dump_flowtable_done+0x70/0x70 [nf_tables]
[ 916.506774] ? nft_obj_notify+0x100/0x100 [nf_tables]
[ 916.514808] nfnetlink_rcv_msg+0x8ab/0xa86 [nfnetlink]
[ 916.518771] ? nfnetlink_rcv_msg+0x550/0xa86 [nfnetlink]
[ 916.526782] netlink_rcv_skb+0x23e/0x360
[ 916.530773] ? nfnetlink_bind+0x200/0x200 [nfnetlink]
[ 916.534778] ? debug_check_no_locks_freed+0x280/0x280
[ 916.542770] ? netlink_ack+0x870/0x870
[ 916.546786] ? ns_capable_common+0xf4/0x130
[ 916.550765] nfnetlink_rcv+0x172/0x16c0 [nfnetlink]
[ 916.554771] ? sched_clock_local+0xe2/0x150
[ 916.558774] ? sched_clock_cpu+0x144/0x180
[ 916.566575] ? lock_acquire+0x380/0x380
[ 916.570775] ? sched_clock_local+0xe2/0x150
[ 916.574765] ? nfnetlink_net_init+0x130/0x130 [nfnetlink]
[ 916.578763] ? sched_clock_cpu+0x144/0x180
[ 916.582770] ? lock_acquire+0x193/0x380
[ 916.590771] ? lock_acquire+0x193/0x380
[ 916.594766] ? lock_acquire+0x380/0x380
[ 916.598760] ? netlink_deliver_tap+0x262/0xa60
[ 916.602766] ? lock_acquire+0x193/0x380
[ 916.606766] netlink_unicast+0x3ef/0x5a0
[ 916.610771] ? netlink_attachskb+0x630/0x630
[ 916.614763] netlink_sendmsg+0x72a/0xb00
[ 916.618769] ? netlink_unicast+0x5a0/0x5a0
[ 916.626766] ? _copy_from_user+0x92/0xc0
[ 916.630773] __sys_sendto+0x202/0x300
[ 916.634772] ? __ia32_sys_getpeername+0xb0/0xb0
[ 916.638759] ? lock_acquire+0x380/0x380
[ 916.642769] ? lock_acquire+0x193/0x380
[ 916.646761] ? finish_task_switch+0xf4/0x560
[ 916.650763] ? __schedule+0x582/0x19a0
[ 916.655301] ? __sched_text_start+0x8/0x8
[ 916.655301] ? up_read+0x1c/0x110
[ 916.655301] ? __do_page_fault+0x48b/0xaa0
[ 916.655301] ? entry_SYSCALL_64_after_hwframe+0x59/0xbe
[ 916.655301] __x64_sys_sendto+0xdd/0x1b0
[ 916.655301] do_syscall_64+0x96/0x3d0
[ 916.655301] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 916.655301] RIP: 0033:0x7f57a0ff5e03
[ 916.655301] RSP: 002b:00007fff6367e0a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[ 916.655301] RAX: ffffffffffffffda RBX: 00007fff6367f1e0 RCX: 00007f57a0ff5e03
[ 916.655301] RDX: 0000000000000020 RSI: 00007fff6367e110 RDI: 0000000000000003
[ 916.655301] RBP: 00007fff6367e100 R08: 00007f57a0ce9160 R09: 000000000000000c
[ 916.655301] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff6367e110
[ 916.655301] R13: 0000000000000020 R14: 00007f57a153c610 R15: 0000562417258de0
[ 916.655301] Code: ff ff ff 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 fa 53 48 c1 ea 03 48 b8 00 00 00 00 00 fc ff df 48 89 fd 48 83 ec 08 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f
[ 916.655301] RIP: strlen+0x1a/0x90 RSP: ffff88010ff0f2f8
[ 916.771929] ---[ end trace 1065e048e72479fe ]---
[ 916.777204] Kernel panic - not syncing: Fatal exception
[ 916.778158] Kernel Offset: 0x14000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)

Signed-off-by: Taehee Yoo <ap420073@xxxxxxxxx>
Acked-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
net/netfilter/nft_ct.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -875,22 +875,26 @@ static int nft_ct_helper_obj_dump(struct
struct nft_object *obj, bool reset)
{
const struct nft_ct_helper_obj *priv = nft_obj_data(obj);
- const struct nf_conntrack_helper *helper = priv->helper4;
+ const struct nf_conntrack_helper *helper;
u16 family;

+ if (priv->helper4 && priv->helper6) {
+ family = NFPROTO_INET;
+ helper = priv->helper4;
+ } else if (priv->helper6) {
+ family = NFPROTO_IPV6;
+ helper = priv->helper6;
+ } else {
+ family = NFPROTO_IPV4;
+ helper = priv->helper4;
+ }
+
if (nla_put_string(skb, NFTA_CT_HELPER_NAME, helper->name))
return -1;

if (nla_put_u8(skb, NFTA_CT_HELPER_L4PROTO, priv->l4proto))
return -1;

- if (priv->helper4 && priv->helper6)
- family = NFPROTO_INET;
- else if (priv->helper6)
- family = NFPROTO_IPV6;
- else
- family = NFPROTO_IPV4;
-
if (nla_put_be16(skb, NFTA_CT_HELPER_L3PROTO, htons(family)))
return -1;