BKL use in ptrace

BKL use in ptrace

[Andi Kleen]

Hi,

ptrace has this comment/BKL use:

        /*
         * This lock_kernel fixes a subtle race with suid exec
         */
        lock_kernel();

But unless I'm blind I don't see execve actually getting the BKL
anywhere. So is this comment outdated or misleading (is the race with exit?)
or is there a bug?

Thanks,
-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.

Re: BKL use in ptrace

[Oleg Nesterov]

(add Roland)

On 12/20, Andi Kleen wrote:
>
> ptrace has this comment/BKL use:
>
>         /*
>          * This lock_kernel fixes a subtle race with suid exec
>          */
>         lock_kernel();
>
> But unless I'm blind I don't see execve actually getting the BKL
> anywhere. So is this comment outdated or misleading (is the race with exit?)
> or is there a bug?

I never understood this lock_kernel().

In any case it looks outdated. We were going to kill it "soon",
along with other ptrace changes.

Oleg.

Re: BKL use in ptrace

[Roland McGrath]

> I never understood this lock_kernel().
> 
> In any case it looks outdated. We were going to kill it "soon",
> along with other ptrace changes.

I never understood it either.  It's very ancient and long predates many,
many ptrace cleanups.  If the comment was ever accurate, then any issue
like that is now covered by cred_guard_mutex.  I don't know of any reason
for (or really, effect of) using BKL in ptrace.


Thanks,
Roland