Re: + fully-honor-vdso_enabled.patch added to -mm tree

[Chuck Ebbert]

John Reiser wrote:
> The value of ->sysenter_return is interpreted in user space by the
> sysexit instruction; nobody else cares what the value is.  The kernel
> is not required to provide a good value when vdso_enabled is zero,
> because the kernel has not told the process that sysenter is valid
> (by setting AT_SYSINFO.)

Doesn't matter because a malicious user can still execute sysenter.
We do have to deal with that somehow, so we have to put something
safe in there.

> Correct.  Changing vdso_enabled from 0 to non-zero must be prepared
> to lose this race if it is not prevented.  Ordinarily it won't matter
> because the administrator will perform such changes at a "quiet" time.
> 

We have to deal with all the possibilities here, too.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/