Date: Thu, 18 Feb 2010 10:23:36 +0800 From: Eugene Teo <eugene@...hat.com> To: oss-security@...ts.openwall.com CC: dann frazier <dannf@...nf.org>, "Steven M. Christey" <coley@...us.mitre.org> Subject: Re: CVE request - kernel: DoS on x86_64 On 02/05/2010 06:46 AM, dann frazier wrote: > On Thu, Feb 04, 2010 at 01:09:09PM +0800, Eugene Teo wrote: >> On 02/04/2010 10:28 AM, dann frazier wrote: >>> On Mon, Feb 01, 2010 at 01:09:12PM +0800, Eugene Teo wrote: >>>> Reported by Mathias Krause. The problem seams to be located in >>>> fs/binfmt_elf.c:load_elf_binary(). It calls SET_PERSONALITY() prior >>>> checking that the ELF interpreter is available. This in turn makes the >>>> previously 32 bit process a 64 bit one which would be fine if execve() >>>> would succeed. But after the SET_PERSONALITY() the open_exec() call >>>> fails (because it cannot find the interpreter) and execve() almost >>>> instantly returns with an error. If you now look at /proc/PID/maps >>>> you'll see, that it has the vsyscall page mapped which shouldn't be. But >>>> the process is not dead yet, it's still running. By now generating a >>>> segmentation fault and in turn trying to generate a core dump the >>>> kernel just dies. >>>> >>>> Steps to Reproduce: >>>> 1. Enable core dumps >>>> 2. Start an 32 bit program that tries to execve() an 64 bit program >>>> 3. The 64 bit program cannot be started by the kernel because it can't >>>> find the interpreter, i.e. execve returns with an error >>>> 4. Generate a segmentation fault >>>> 5. panic >>>> >>>> Upstream commit: >>>> http://git.kernel.org/linus/221af7f87b97431e3ee21ce4b0e77d5411cf1549 >>> >>> Thanks Eugene. >>> >>> Also note this fix for a regression in the above: >>> http://git.kernel.org/linus/7ab02af428c2d312c0cf8fb0b01cc1eb21131a3d >> >> Ben Hutchings reported (via stable review list) that the fix did not >> work for him. Will monitor the list if there are other follow-ups. > > Indeed, it also needs this change for x86: > http://git.kernel.org/linus/05d43ed8a89c159ff641d472f970e3f1baa66318 > > And the corresponding changes for powerpc& sparc: > http://git.kernel.org/linus/94f28da8409c6059135e89ac64a0839993124155 > http://git.kernel.org/linus/94673e968cbcce07fa78dac4b0ae05d24b5816e1 > > All are in queue-2.6.32 now, btw. Here's my updated list of patches to backport for this vulnerability: - 221af7f87 ("Split 'flush_old_exec' into two functions") - 05d43ed8a ("x86: get rid of the insane TIF_ABI_PENDING bit") - 7ab02af42 ("Fix 'flush_old_exec()/setup_new_exec()' split") - 94f28da84 ("powerpc: TIF_ABI_PENDING bit removal") - 1252f238d ("x86: set_personality_ia32() misses force_personality32") Thanks, Eugene -- Eugene Teo / Red Hat Security Response Team
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