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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
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

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04  7:15 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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