Re: [RFC] net,socket: introduce build_sockaddr_check helper to catch overflow at build time

[Cyrill Gorcunov <gorcunov@gmail.com>]

[David Miller - Thu, Oct 22, 2009 at 04:49:14AM -0700]
| From: Cyrill Gorcunov <gorcunov@gmail.com>
| Date: Wed, 21 Oct 2009 21:07:32 +0400
| 
| > net,socket: introduce build_sockaddr_check helper to catch overflow at build time
| > 
| > proto_ops->getname implies copying protocol specific data
| > into storage unit (particulary to __kernel_sockaddr_storage).
| > So when one implements new protocol he either may keep this
| > in mind (or may not).
| > 
| > Lets introduce build_sockaddr_check helper which check if
| > storage unit is not overfowed. Note that the check is build
| > time and introduce no slowdown at execution time.
| > 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
| 
| Nice idea, and I wonder if we can automate it even further.
| Perhaps some tag that gets put on the socket address type
| definition or similar?
| 

Thanks for review David! Not sure if I understand you right.
Initially I was trying to bring as minimum changes as possible.
Also I was shuffle in mind the following possibilities:

1) Since at least one .getname handler use memcpy, we could
   introduce some helper which check size (at build time) and
   then do memcpy (not optimal perhaps).


2) All handlers set *len to some size explicitly so we may
   introduce set_sockaddr_size() helper like

#define set_sockaddr_size(ptr, size)		\
	do {					\
		build_sockaddr_check(size);	\
		*ptr = size;			\
	} while (0)

Or you meant something completely different?

	-- Cyrill