Re: [PATCH 4.4 02/96] s390/runtime instrumention: fix possible memory corruption

[Ben Hutchings]

On Tue, 2017-11-28 at 11:22 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.ÂÂIf anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> 
> commit d6e646ad7cfa7034d280459b2b2546288f247144 upstream.
[...]
> --- a/arch/s390/kernel/runtime_instr.c
> +++ b/arch/s390/kernel/runtime_instr.c
> @@ -47,11 +47,13 @@ void exit_thread_runtime_instr(void)
> Â{
> Â	struct task_struct *task = current;
> Â
> +	preempt_disable();
> Â	if (!task->thread.ri_cb)
> Â		return;

This return path now leaves preemption disabled.  This seems to have
been fixed upstream by commit 8d9047f8b967 "s390/runtime
instrumentation: simplify task exit handling".

Ben.

> Â	disable_runtime_instr();
> Â	kfree(task->thread.ri_cb);
> Â	task->thread.ri_cb = NULL;
> +	preempt_enable();
> Â}
> Â
> ÂSYSCALL_DEFINE1(s390_runtime_instr, int, command)
[...]

-- 
Ben Hutchings
Software Developer, Codethink Ltd.