Re: Compat 32-bit syscall entry from 64-bit task!?

[Will Drewry]

On Wed, Jan 18, 2012 at 1:47 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Jan 18, 2012 at 11:44 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>>
>> It can securely enable syscall auditing which can catch all syscalls
>> (however you only get race free memory arguments for the ones with LSM hooks
>> at the right place). Really need both.
>>
>> I agree it's not easy to get tight (and also not pretty), but you have a lot
>> better chance doing it this way than with ptrace.
>
> .. And how the f*^& did you imagine that something like chrome would do that?
>
> You need massive amounts of privileges, and it's a total disaster in
> every single respect.
>
> Stop pushing crap. No, ptrace isn't wonderful, but your LSM+auditing
> idea is a billion times worse in all respects.
>
> We can definitely fix the ptrace issue with compat system calls.

FWIW, it looks like audit needs fixing too.  If a process only uses
TIF_SYSCALL_AUDIT, then the fast-path will properly annotate the entry
with AUDIT_ARCH_I386, but if it takes the slow path because of some
other tracing on a thread (ftrace, ptrace, ...), then the audit record
will incorrectly use TIF_IA32 to write the audit record.  Easy patch
(I'll write it up shortly), but yet another case of breakage.
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