[PATCH 3.14 74/78] netfilter: nfnetlink: Fix use after free when it fails to process batch

Greg Kroah-Hartman
2014-06-09T22:51:56Z

From: Denys Fedoryshchenko <nuclearcat@nuclearcat.com>

commit ecd15dd7e45f3683fa8142b9f2c015dfaa0c243d upstream.

This bug manifests when calling the nft command line tool without
nf_tables kernel support.

kernel message:
[ 44.071555] Netfilter messages via NETLINK v0.30.
[ 44.072253] BUG: unable to handle kernel NULL pointer dereference at 0000000000000119
[ 44.072264] IP: [<ffffffff8171db1f>] netlink_getsockbyportid+0xf/0x70
[ 44.072272] PGD 7f2b74067 PUD 7f2b73067 PMD 0
[ 44.072277] Oops: 0000 [#1] SMP
[...]
[ 44.072369] Call Trace:
[ 44.072373] [<ffffffff8171fd81>] netlink_unicast+0x91/0x200
[ 44.072377] [<ffffffff817206c9>] netlink_ack+0x99/0x110
[ 44.072381] [<ffffffffa004b951>] nfnetlink_rcv+0x3c1/0x408 [nfnetlink]
[ 44.072385] [<ffffffff8171fde3>] netlink_unicast+0xf3/0x200
[ 44.072389] [<ffffffff817201ef>] netlink_sendmsg+0x2ff/0x740
[ 44.072394] [<ffffffff81044752>] ? __mmdrop+0x62/0x90
[ 44.072398] [<ffffffff816dafdb>] sock_sendmsg+0x8b/0xc0
[ 44.072403] [<ffffffff812f1af5>] ? copy_user_enhanced_fast_string+0x5/0x10
[ 44.072406] [<ffffffff816dbb6c>] ? move_addr_to_kernel+0x2c/0x50
[ 44.072410] [<ffffffff816db423>] ___sys_sendmsg+0x3c3/0x3d0
[ 44.072415] [<ffffffff811301ba>] ? handle_mm_fault+0xa9a/0xc60
[ 44.072420] [<ffffffff811362d6>] ? mmap_region+0x166/0x5a0
[ 44.072424] [<ffffffff817da84c>] ? __do_page_fault+0x1dc/0x510
[ 44.072428] [<ffffffff812b8b2c>] ? apparmor_capable+0x1c/0x60
[ 44.072435] [<ffffffff817d6e9a>] ? _raw_spin_unlock_bh+0x1a/0x20
[ 44.072439] [<ffffffff816dfc86>] ? release_sock+0x106/0x150
[ 44.072443] [<ffffffff816dc212>] __sys_sendmsg+0x42/0x80
[ 44.072446] [<ffffffff816dc262>] SyS_sendmsg+0x12/0x20
[ 44.072450] [<ffffffff817df616>] system_call_fastpath+0x1a/0x1f

Signed-off-by: Denys Fedoryshchenko <nuclearcat@nuclearcat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/nfnetlink.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -248,15 +248,15 @@ replay:
#endif
{
nfnl_unlock(subsys_id);
- kfree_skb(nskb);
- return netlink_ack(skb, nlh, -EOPNOTSUPP);
+ netlink_ack(skb, nlh, -EOPNOTSUPP);
+ return kfree_skb(nskb);
}
}

if (!ss->commit || !ss->abort) {
nfnl_unlock(subsys_id);
- kfree_skb(nskb);
- return netlink_ack(skb, nlh, -EOPNOTSUPP);
+ netlink_ack(skb, nlh, -EOPNOTSUPP);
+ return kfree_skb(skb);
}

while (skb->len >= nlmsg_total_size(0)) {