On Fri, Jun 17, 2016 at 12:15 AM, James Morris <jmor...@namei.org> wrote:
> On Tue, 14 Jun 2016, Kees Cook wrote:
>
>> Hi,
>>
>> Please pull these seccomp changes for next. These have been tested by
>> myself and Andy, and close a long-standing issue with seccomp where tracers
>> could change the syscall out from under seccomp.
>
> Pulled to security -next.
As a heads up: I think this doesn't quite close the hole on x86. Consider:
64-bit task arranges to be traced by a 32-bit task (or presumably a
64-bit task that calls ptrace via int80).
Tracer does PTRACE_SYSCALL.
Tracee does a normal syscall.
Tracer writes tracee's orig_ax, thus invoking this thing in
arch/x86/kernel/ptrace.c:
if (syscall_get_nr(child, regs) >= 0)
child->thread.status |= TS_COMPAT;
Tracer resumes and gets confused.
I think the right fix is to just delete:
if (syscall_get_nr(child, regs) >= 0)
child->thread.status |= TS_COMPAT;
from ptrace.c. The comment above it is garbage, too.
--Andy
