From: David Ashley <dash@xdr•com>
To: bcrl@redhat•com
Cc: linuxppc-embedded@lists•linuxppc.org
Subject: Re: mmap wrapping around to 0 revisited
Date: Tue, 5 Mar 2002 16:06:42 -0800 [thread overview]
Message-ID: <200203060006.g2606g123689@xdr.com> (raw)
>Wrong fix. sys_mmap on ppc should really be using do_mmap which already
>includes the cast to unsigned long and checks for overflow. Arguably,
>it could well check for -'ve offsets and reject them, but traditionally
>Linux has accepted up to 4GB offsets with its 32 bit APIs and changing
>this would break a few things like X.
>
> -ben
In older versions (like 2.4.2-hhl) the sys_mmap did go through do_mmap, but
for some reason that was changed. The do_mmap itself is broken, the check
for overflow is like this:
if ((offset + PAGE_ALIGN(len)) < offset)
goto out;
It should be:
if ((offset + PAGE_ALIGN(len)-1) < offset)
goto out;
So: changing sys_mmap to go through do_mmap won't fix the problem unless
the above fix is done to do_mmap.
do_mmap appears to be defunct, and the new method seems to be more standard
across architectures. The problem was as I stated, and the fix I presented
is the best one.
-Dave
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next reply other threads:[~2002-03-06 0:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-06 0:06 David Ashley [this message]
2002-03-05 23:58 ` mmap wrapping around to 0 revisited Dan Malek
-- strict thread matches above, loose matches on Subject: below --
2002-03-07 2:37 David Ashley
2002-03-04 16:05 David Ashley
2002-03-05 20:47 ` Benjamin LaHaise
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