Date: Wed, 18 Jan 2012 12:43:28 -0800 From: Kees Cook <kees@...ntu.com> To: oss-security@...ts.openwall.com Cc: "Steven M. Christey" <coley@...us.mitre.org> Subject: Re: CVE request: kernel: proc: clean up and fix /proc/<pid>/mem handling What's the problem with the old logic in the mem handling? (Why does this need a CVE?) On Wed, Jan 18, 2012 at 10:25:55AM +0800, Eugene Teo wrote: > "Jüri Aedla reported that the /proc/<pid>/mem handling really isn't very > robust, and it also doesn't match the permission checking of any of the > other related files. > > This changes it to do the permission checks at open time, and instead of > tracking the process, it tracks the VM at the time of the open. That > simplifies the code a lot, but does mean that if you hold the file > descriptor open over an execve(), you'll continue to read from the _old_ VM. > > That is different from our previous behavior, but much simpler. If > somebody actually finds a load where this matters, we'll need to revert > this commit. > > I suspect that nobody will ever notice - because the process mapping > addresses will also have changed as part of the execve. So you cannot > actually usefully access the fd across a VM change simply because all > the offsets for IO would have changed too." > > http://git.kernel.org/linus/e268337dfe26dfc7efd422a804dbb27977a3cccc > > Thanks, Eugene -- Kees Cook
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