[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <4A5ECD5E.8060901@redhat.com>
Date: Thu, 16 Jul 2009 14:49:02 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: "Steven M. Christey" <coley@...us.mitre.org>
Subject: CVE-2009-1895 kernel: personality: fix PER_CLEAR_ON_SETID
Reported by Julien Tinnes.
"We have found that the current PER_CLEAR_ON_SETID mask on Linux doesn't
include neither ADDR_COMPAT_LAYOUT, nor MMAP_PAGE_ZERO.
The current mask is READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE.
We believe it is important to add MMAP_PAGE_ZERO, because by using this
personality it is possible to have the first page mapped inside a
process running as setuid root. This could be used in those scenarios:
- Exploiting a NULL pointer dereference issue in a setuid root binary
- Bypassing the mmap_min_addr restrictions of the Linux kernel: by
running a setuid binary that would drop privileges before giving us
control back (for instance by loading a user-supplied library), we could
get the first page mapped in a process we control. By further using
mremap and mprotect on this mapping, we can then completely bypass the
mmap_min_addr restrictions.
Less importantly, we believe ADDR_COMPAT_LAYOUT should also be added
since on x86 32bits it will in practice disable most of the address
space layout randomization (only the stack will remain randomized)."
Upstream commit:
http://git.kernel.org/linus/f9fabcb58a6d26d6efde842d1703ac7cfa9427b6
References:
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2009-1895
http://blog.cr0.org/2009/06/bypassing-linux-null-pointer.html
http://patchwork.kernel.org/patch/32598/
http://marc.info/?l=linux-security-module&m=124724852000951&w=2
Thanks, Eugene
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
