netdev - Re: af_unix unix_getname: return size for unnamed sockets too small?

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Date:	Wed, 02 Feb 2011 10:59:30 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Marcus Meissner <meissner@...e.de>
Cc:	davem@...emloft.net, eric.dumazet@...il.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	gorcunov@...nvz.org
Subject: Re: af_unix unix_getname: return size for unnamed sockets too small?

Marcus Meissner <meissner@...e.de> writes:

> Hi,
>
> In net/unix/af_unix.c::unix_getname() there is a small problem:
>
>         if (!u->addr) {
>                 sunaddr->sun_family = AF_UNIX;
>                 sunaddr->sun_path[0] = 0;		// not copied out
>                 *uaddr_len = sizeof(short);
>         } else {
>                 struct unix_address *addr = u->addr;
>
>                 *uaddr_len = addr->len;
>                 memcpy(sunaddr, addr->name, *uaddr_len);
>         }
>
> The if (!u->addr) case will not copy out the \0 in the sun_path, as
> uaddr_len is just the size of sun_family.
>
> (Shown by socat crashing after decoding gethostname return and expected
> sun_path to be a valid string (and not seeing the \0)).

Perhaps my memory is scrambled but the sun_path has embedded '\0's so I
don't see how a correct application can expect the path to be '\0'
terminated.  An application should be looking at the length we give it.

> Should it perhaps be *uaddr_len = sizeof(short)+sizeof(char)?

I don't think so.

Eric

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