netdev - [PATCH 11/12] netfilter: nf_tables: fix out-of-bounds in nft_chain_commit

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Message-Id: <20180423175714.9794-12-pablo@netfilter.org>
Date:   Mon, 23 Apr 2018 19:57:13 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 11/12] netfilter: nf_tables: fix out-of-bounds in nft_chain_commit_update

From: Taehee Yoo <ap420073@...il.com>

When chain name is changed, nft_chain_commit_update is called.
In the nft_chain_commit_update, trans->ctx.chain->name has old chain name
and nft_trans_chain_name(trans) has new chain name.
If new chain name is longer than old chain name, KASAN warns
slab-out-of-bounds.

[  175.015012] BUG: KASAN: slab-out-of-bounds in strcpy+0x9e/0xb0
[  175.022735] Write of size 1 at addr ffff880114e022da by task iptables-compat/1458

[  175.031353] CPU: 0 PID: 1458 Comm: iptables-compat Not tainted 4.16.0-rc7+ #146
[  175.031353] 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
[  175.031353] Call Trace:
[  175.031353]  dump_stack+0x68/0xa0
[  175.031353]  print_address_description+0xd0/0x260
[  175.031353]  ? strcpy+0x9e/0xb0
[  175.031353]  kasan_report+0x234/0x350
[  175.031353]  __asan_report_store1_noabort+0x1c/0x20
[  175.031353]  strcpy+0x9e/0xb0
[  175.031353]  nf_tables_commit+0x1ccc/0x2990
[  175.031353]  nfnetlink_rcv+0x141e/0x16c0
[  175.031353]  ? nfnetlink_net_init+0x150/0x150
[  175.031353]  ? lock_acquire+0x370/0x370
[  175.031353]  ? lock_acquire+0x370/0x370
[  175.031353]  netlink_unicast+0x444/0x640
[  175.031353]  ? netlink_attachskb+0x700/0x700
[  175.031353]  ? _copy_from_iter_full+0x180/0x740
[  175.031353]  ? kasan_check_write+0x14/0x20
[  175.031353]  ? _copy_from_user+0x9b/0xd0
[  175.031353]  netlink_sendmsg+0x845/0xc70
[ ... ]

Steps to reproduce:
   iptables-compat -N 1
   iptables-compat -E 1 aaaaaaaaa

Signed-off-by: Taehee Yoo <ap420073@...il.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_tables_api.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 102ad873acb4..04d4e3772584 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5745,7 +5745,7 @@ static void nft_chain_commit_update(struct nft_trans *trans)
 	struct nft_base_chain *basechain;
 
 	if (nft_trans_chain_name(trans))
-		strcpy(trans->ctx.chain->name, nft_trans_chain_name(trans));
+		swap(trans->ctx.chain->name, nft_trans_chain_name(trans));
 
 	if (!nft_is_base_chain(trans->ctx.chain))
 		return;
-- 
2.11.0