From: Leon Romanovsky <leon@kernel.org>
To: Or Cohen <orcohen@paloaltonetworks.com>
Cc: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org,
nixiaoming@huawei.com, matthieu.baerts@tessares.net,
mkl@pengutronix.de, nmarkus@paloaltonetworks.com
Subject: Re: [PATCH] net/nfc: fix use-after-free llcp_sock_bind/connect
Date: Tue, 4 May 2021 11:12:27 +0300 [thread overview]
Message-ID: <YJEB6+K0RaPg8KD6@unreal> (raw)
In-Reply-To: <20210504071525.28342-1-orcohen@paloaltonetworks.com>
On Tue, May 04, 2021 at 10:15:25AM +0300, Or Cohen wrote:
> Commits 8a4cd82d ("nfc: fix refcount leak in llcp_sock_connect()")
> and c33b1cc62 ("nfc: fix refcount leak in llcp_sock_bind()")
> fixed a refcount leak bug in bind/connect but introduced a
> use-after-free if the same local is assigned to 2 different sockets.
>
> This can be triggered by the following simple program:
> int sock1 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP );
> int sock2 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP );
> memset( &addr, 0, sizeof(struct sockaddr_nfc_llcp) );
> addr.sa_family = AF_NFC;
> addr.nfc_protocol = NFC_PROTO_NFC_DEP;
> bind( sock1, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) )
> bind( sock2, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) )
> close(sock1);
> close(sock2);
>
> Fix this by assigning NULL to llcp_sock->local after calling
> nfc_llcp_local_put.
>
> This addresses CVE-2021-23134.
>
> Reported-by: Or Cohen <orcohen@paloaltonetworks.com>
> Reported-by: Nadav Markus <nmarkus@paloaltonetworks.com>
> Fixes: c33b1cc62 ("nfc: fix refcount leak in llcp_sock_bind()")
> Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
> ---
>
> net/nfc/llcp_sock.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
> index a3b46f888803..53dbe733f998 100644
> --- a/net/nfc/llcp_sock.c
> +++ b/net/nfc/llcp_sock.c
> @@ -109,12 +109,14 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
> GFP_KERNEL);
> if (!llcp_sock->service_name) {
> nfc_llcp_local_put(llcp_sock->local);
> + llcp_sock->local = NULL;
This "_put() -> set to NULL" pattern can't be correct.
You need to fix nfc_llcp_local_get() to use kref_get_unless_zero()
and prevent any direct use of llcp_sock->local without taking kref
first. The nfc_llcp_local_put() isn't right either.
Thanks
next prev parent reply other threads:[~2021-05-04 8:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-04 7:15 [PATCH] net/nfc: fix use-after-free llcp_sock_bind/connect Or Cohen
2021-05-04 8:12 ` Leon Romanovsky [this message]
2021-05-04 16:01 ` Or Cohen
2021-05-05 4:46 ` Leon Romanovsky
[not found] ` <CABV_C9OJ6v1deEknc+V3cJaT+CPjmzg6Wb06_Rsey3AXqOBNYg@mail.gmail.com>
2021-05-05 11:30 ` Nadav Markus
2021-05-05 11:39 ` Leon Romanovsky
[not found] ` <CABV_C9PscjqNPTbK0JuNGsgCAX-xYg9=GG1KNyOh3hQU1TuzWQ@mail.gmail.com>
2021-05-05 14:17 ` Leon Romanovsky
2021-05-05 14:31 ` Or Cohen
2021-05-04 7:16 Or Cohen
2021-05-04 19:10 ` patchwork-bot+netdevbpf
2021-05-05 4:50 ` Leon Romanovsky
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