netdev - RE: [patch] Fix handling of overlength pathname in AF_UNIX sun

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Date:	Wed, 18 Apr 2012 09:17:26 +0100
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Carlos O'Donell" <carlos@...temhalted.org>,
	"David Miller" <davem@...emloft.net>
Cc:	<mtk.manpages@...il.com>, <netdev@...r.kernel.org>,
	<penguin-kernel@...ove.sakura.ne.jp>, <linux-api@...r.kernel.org>,
	<yoshfuji@...ux-ipv6.org>, <jengelh@...ozas.de>, <w@....eu>,
	<alan@...rguk.ukuu.org.uk>
Subject: RE: [patch] Fix handling of overlength pathname in AF_UNIX sun_path

 
> 
> Why not have:
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index d510353..f9f77a7 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -216,6 +216,9 @@ static int unix_mkname(struct sockaddr_un
> *sunaddr, int len, unsigned *hashp)
>                  */
>                 ((char *)sunaddr)[len] = 0;
>                 len = strlen(sunaddr->sun_path)+1+sizeof(short);
> +               /* No null terminator was found in the path. */
> +               if (len > sizeof(*sunaddr))
> +                       return -EINVAL;
>                 return len;

That could generate a kernel page fault!
(Depending on what follows (or rather doesn't follow!) sun_path.)
You'd need to use memchr() not strlen().

	David


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