[PATCH 4.14 034/189] netfilter: nf_tables: fix out-of-bounds in nft_chain_commit_update

Greg Kroah-Hartman
2018-06-18T08:30:31Z

From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit d71efb599ad42ef1e564c652d8084252bdc85edf ]

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@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4977,7 +4977,7 @@ static void nft_chain_commit_update(stru
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;