linux-kernel - Re: access

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Message-Id: <200907141645.48833.arnd@arndb.de>
Date:	Tue, 14 Jul 2009 16:45:48 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	monstr@...str.eu
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	LTP <ltp-list@...ts.sourceforge.net>
Subject: Re: access_ok macor

On Tuesday 14 July 2009, Michal Simek wrote:
> Arnd Bergmann wrote:
> Look at
> http://developer.petalogix.com/git/gitweb.cgi?p=ltp-microblaze.git;a=commitdiff;h=45f4cd783ce8b94f1267bb87c0c46e8536f62eca
> 
> There are three affected tests and my quick fixes which I am trying to solve now.
> 

ok, I see.
 
> int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uaddr,
> 		      int __user *ulen)
> {
> 	int err;
> 	int len;
> 
> 	err = get_user(len, ulen);
> 	if (err)
> 		return err;
> 

So the code looks something like

                        "1:     lw      %1, %2, r0;                     \
                                addk    %0, r0, r0;                     \
                        2:                                              \
                        .section .fixup,\"ax\";                         \
                        3:      brid    2b;                             \
                                addik   %0, r0, %3;                     \
                        .previous;                                      \
                        .section ,\"a\";                      		\
                        .word   1b,3b;                                  \
                        .previous;"                                     \

Not much that can go wrong there. First of all, I'd check that the
code actually looks the same in the binary. I assume that the 'addik'
gets executed when the brid branches, right?

I would guess that some of the logic in do_page_fault might be
broken and does not actually call the fixup.

	Arnd <><
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