Date: Thu, 2 Dec 2010 11:00:44 -0500 From: Dan Rosenberg <dan.j.rosenberg@...il.com> To: oss-security@...ts.openwall.com Subject: Re: kernel: Dangerous interaction between clear_child_tid, set_fs(), and kernel oopses Please note that this is the issue I was referring to in my previous post. Thanks, list moderators, for the amusing timing. :) -Dan On Thu, Dec 2, 2010 at 12:21 AM, Nelson Elhage <nelhage@...lice.com> wrote: > I've discovered an interesting interaction in the Linux kernel between the > clear_child_tid feature of clone(2), and the set_fs() function used internally > in the kernel to temporarily disable access_ok() checking of userspace pointers. > > Under some (not totally uncommon) circumstances, it is possible for a user to > leverage this interaction to turn a kernel oops or BUG() into a write of an > integer 0 to a user-controlled address in kernel memory. > > I'm not sure if this merits a CVE or not; It is (as far as I can tell) only a > problem in the presence of another security bug, but it potentially makes a > large class of bugs significantly more dangerous (DoS -> privesc). > > Reference: > https://lkml.org/lkml/2010/12/1/543 > > - Nelson >
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