[PATCH v2 net] nfc: close a race condition in llcp_sock_getname()

[PATCH v2 net] nfc: close a race condition in llcp_sock_getname()

[Cong Wang]

llcp_sock_getname() checks llcp_sock->dev to make sure
llcp_sock is already connected or bound, however, we could
be in the middle of llcp_sock_bind() where llcp_sock->dev
is bound and llcp_sock->service_name_len is set,
but llcp_sock->service_name is not, in this case we would
lead to copy some bytes from a NULL pointer.

Just lock the sock since this is not a hot path anyway.

Reported-by: Dmitry Vyukov <dvyukov-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Lauro Ramos Venancio <lauro.venancio-430g2QfJUUCGglJvpFV4uA@public.gmane.org>
Cc: Aloisio Almeida Jr <aloisio.almeida-430g2QfJUUCGglJvpFV4uA@public.gmane.org>
Cc: Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Signed-off-by: Cong Wang <xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 net/nfc/llcp_sock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index ecf0a01..b9edf5f 100644
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -509,6 +509,11 @@ static int llcp_sock_getname(struct socket *sock, struct sockaddr *uaddr,
 	memset(llcp_addr, 0, sizeof(*llcp_addr));
 	*len = sizeof(struct sockaddr_nfc_llcp);
 
+	lock_sock(sk);
+	if (!llcp_sock->dev) {
+		release_sock(sk);
+		return -EBADFD;
+	}
 	llcp_addr->sa_family = AF_NFC;
 	llcp_addr->dev_idx = llcp_sock->dev->idx;
 	llcp_addr->target_idx = llcp_sock->target_idx;
@@ -518,6 +523,7 @@ static int llcp_sock_getname(struct socket *sock, struct sockaddr *uaddr,
 	llcp_addr->service_name_len = llcp_sock->service_name_len;
 	memcpy(llcp_addr->service_name, llcp_sock->service_name,
 	       llcp_addr->service_name_len);
+	release_sock(sk);
 
 	return 0;
 }
-- 
1.8.3.1

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Re: [PATCH v2 net] nfc: close a race condition in llcp_sock_getname()

[Cong Wang]

On Fri, Jan 29, 2016 at 11:37 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> llcp_sock_getname() checks llcp_sock->dev to make sure
> llcp_sock is already connected or bound, however, we could
> be in the middle of llcp_sock_bind() where llcp_sock->dev
> is bound and llcp_sock->service_name_len is set,
> but llcp_sock->service_name is not, in this case we would
> lead to copy some bytes from a NULL pointer.
>
> Just lock the sock since this is not a hot path anyway.
>
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
> Cc: Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
> Cc: Samuel Ortiz <sameo@linux.intel.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>


Samuel, please take a look at this one too.


> ---
>  net/nfc/llcp_sock.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
> index ecf0a01..b9edf5f 100644
> --- a/net/nfc/llcp_sock.c
> +++ b/net/nfc/llcp_sock.c
> @@ -509,6 +509,11 @@ static int llcp_sock_getname(struct socket *sock, struct sockaddr *uaddr,
>         memset(llcp_addr, 0, sizeof(*llcp_addr));
>         *len = sizeof(struct sockaddr_nfc_llcp);
>
> +       lock_sock(sk);
> +       if (!llcp_sock->dev) {
> +               release_sock(sk);
> +               return -EBADFD;
> +       }
>         llcp_addr->sa_family = AF_NFC;
>         llcp_addr->dev_idx = llcp_sock->dev->idx;
>         llcp_addr->target_idx = llcp_sock->target_idx;
> @@ -518,6 +523,7 @@ static int llcp_sock_getname(struct socket *sock, struct sockaddr *uaddr,
>         llcp_addr->service_name_len = llcp_sock->service_name_len;
>         memcpy(llcp_addr->service_name, llcp_sock->service_name,
>                llcp_addr->service_name_len);
> +       release_sock(sk);
>
>         return 0;
>  }
> --
> 1.8.3.1
>

Re: [PATCH v2 net] nfc: close a race condition in llcp_sock_getname()

[Samuel Ortiz]

Hi Cong,

On Fri, Jan 29, 2016 at 11:37:40AM -0800, Cong Wang wrote:
> llcp_sock_getname() checks llcp_sock->dev to make sure
> llcp_sock is already connected or bound, however, we could
> be in the middle of llcp_sock_bind() where llcp_sock->dev
> is bound and llcp_sock->service_name_len is set,
> but llcp_sock->service_name is not, in this case we would
> lead to copy some bytes from a NULL pointer.
> 
> Just lock the sock since this is not a hot path anyway.
> 
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
> Cc: Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
> Cc: Samuel Ortiz <sameo@linux.intel.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
>  net/nfc/llcp_sock.c | 6 ++++++
>  1 file changed, 6 insertions(+)
Applied as well, thanks.

Cheers,
Samuel.