[PATCH 5.10.y v2] Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"

[Greg KH]

On Mon, Feb 19, 2024 at 05:57:07PM +0100, Ard Biesheuvel wrote:
> On Mon, 19 Feb 2024 at 14:24, Xiang Yang <xiangyang3 at huawei.com> wrote:
> >
> > This reverts commit 3f225f29c69c13ce1cbdb1d607a42efeef080056.
> >
> > The shadow call stack for irq now is stored in current task's thread info
> > in irq_stack_entry. There is a possibility that we have some soft irqs
> > pending at the end of hard irq, and when we process softirq with the irq
> > enabled, irq_stack_entry will enter again and overwrite the shadow call
> > stack whitch stored in current task's thread info, leading to the
> > incorrect shadow call stack restoration for the first entry of the hard
> > IRQ, then the system end up with a panic.
> >
> > task A                               |  task A
> > -------------------------------------+------------------------------------
> > el1_irq        //irq1 enter          |
> >   irq_handler  //save scs_sp1        |
> >     gic_handle_irq                   |
> >     irq_exit                         |
> >       __do_softirq                   |
> >                                      | el1_irq         //irq2 enter
> >                                      |   irq_handler   //save scs_sp2
> >                                      |                 //overwrite scs_sp1
> >                                      |   ...
> >                                      |   irq_stack_exit //restore scs_sp2
> >   irq_stack_exit //restore wrong     |
> >                  //scs_sp2           |
> >
> > So revert this commit to fix it.
> >
> > Fixes: 3f225f29c69c ("arm64: Stash shadow stack pointer in the task struct on interrupt")
> >
> > Signed-off-by: Xiang Yang <xiangyang3 at huawei.com>
> 
> Acked-by: Ard Biesheuvel <ardb at kernel.org>

Now queued up, thanks.

greg k-h