oss-sec mailing list archives
Re: CVE-2014-4699: Linux ptrace bug
From: Solar Designer <solar () openwall com>
Date: Sat, 5 Jul 2014 23:35:37 +0400
Andy, all - On Sat, Jul 05, 2014 at 10:25:47PM +0400, Solar Designer wrote:
"x86_64,ptrace: Enforce RIP <= TASK_SIZE_MAX (CVE-2014-4699)"
[...]
"CVE-2014-4699 Kernel: x86_64,ptrace: Enforce RIP <= TASK_SIZE_MAX"
BTW, I'm not convinced it's such a good idea to allow setting RIP to exactly TASK_SIZE_MAX just because user code could run to that address (this was Andy's rationale). Imagine that TASK_SIZE_MAX is ever set such that it's the very first non-canonical address. If user code simply runs to that address, it gets a user mode fault. However, if the kernel tries to set user RIP to that address via SYSRET, it'll get #GP while still in kernel mode - exactly the problem we're trying to fix. So when fixing the problem in this way, or when including this as a hardening measure along with forcing the IRET path as well, I'd prefer to allow only "< TASK_SIZE_MAX", not "<= TASK_SIZE_MAX". I think currently TASK_SIZE_MAX is below the first non-canonical address, so we're fine, but there's little reason to take the risk of possible (valid) future changes to TASK_SIZE_MAX. Alexander
Current thread:
- CVE-2014-4699: Linux ptrace bug Andy Lutomirski (Jul 04)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 04)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Yves-Alexis Perez (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Yves-Alexis Perez (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Yves-Alexis Perez (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Yves-Alexis Perez (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug Andy Lutomirski (Jul 08)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 08)
- Re: CVE-2014-4699: Linux ptrace bug Marc Deslauriers (Jul 05)
- Re: CVE-2014-4699: Linux ptrace bug John Johansen (Jul 06)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 06)
- Re: CVE-2014-4699: Linux ptrace bug John Johansen (Jul 06)
- Re: CVE-2014-4699: Linux ptrace bug Solar Designer (Jul 08)