On Tue, Jan 17, 2023 at 04:56:19PM +0000, Lee Jones wrote: > On Thu, 05 Jan 2023, Greg KH wrote: > > > On Wed, Jan 04, 2023 at 05:32:18PM +0100, Ard Biesheuvel wrote: > > > On Wed, 4 Jan 2023 at 17:30, Mark Rutland <mark.rutland@xxxxxxx> wrote: > > > > > > > > On Wed, Jan 04, 2023 at 05:15:34PM +0100, Ard Biesheuvel wrote: > > > > > On Wed, 4 Jan 2023 at 17:13, Mark Rutland <mark.rutland@xxxxxxx> wrote: > > > > > > > > > > > > On Wed, Jan 04, 2023 at 02:56:19PM +0100, Ard Biesheuvel wrote: > > > > > > > On Wed, 4 Jan 2023 at 11:40, Lee Jones <lee@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On Mon, 05 Dec 2022, Ard Biesheuvel wrote: > > > > > > > > > > > > > > > > > With the introduction of PRMT in the ACPI subsystem, the EFI rts > > > > > > > > > workqueue is no longer the only caller of efi_call_virt_pointer() in the > > > > > > > > > kernel. This means the EFI runtime services lock is no longer sufficient > > > > > > > > > to manage concurrent calls into firmware, but also that firmware calls > > > > > > > > > may occur that are not marshalled via the workqueue mechanism, but > > > > > > > > > originate directly from the caller context. > > > > > > > > > > > > > > > > > > For added robustness, and to ensure that the runtime services have 8 KiB > > > > > > > > > of stack space available as per the EFI spec, introduce a spinlock > > > > > > > > > protected EFI runtime stack of 8 KiB, where the spinlock also ensures > > > > > > > > > serialization between the EFI rts workqueue (which itself serializes EFI > > > > > > > > > runtime calls) and other callers of efi_call_virt_pointer(). > > > > > > > > > > > > > > > > > > While at it, use the stack pivot to avoid reloading the shadow call > > > > > > > > > stack pointer from the ordinary stack, as doing so could produce a > > > > > > > > > gadget to defeat it. > > > > > > > > > > > > > > > > > > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > > > > > > > --- > > > > > > > > > arch/arm64/include/asm/efi.h | 3 +++ > > > > > > > > > arch/arm64/kernel/efi-rt-wrapper.S | 13 +++++++++- > > > > > > > > > arch/arm64/kernel/efi.c | 25 ++++++++++++++++++++ > > > > > > > > > 3 files changed, 40 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > > > Could we have this in Stable please? > > > > > > > > > > > > > > > > Upstream commit: ff7a167961d1b ("arm64: efi: Execute runtime services from a dedicated stack") > > > > > > > > > > > > > > > > Ard, do we need Patch 2 as well, or can this be applied on its own? > > > > > > > > > > > > > > > > > > > > > > Thanks for the reminder. > > > > > > > > > > > > > > Only patch #1 is needed. It should be applied to v5.10 and later. > > > > > > > > > > > > Hold on, why did this go into mainline when I had an outstanding comment w.r.t. > > > > > > the stack unwinder? > > > > > > > > > > > > From your last reply to me there I was expecting a respin with that fixed. > > > > > > > > > > > > > > > > Apologies for the confusion. > > > > > > > > > > I have a patch for this queued up, but AIUI, that cannot be merged all > > > > > the way back to v5.10, so these need to remain separate changes in any > > > > > case. > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c2530a04a73e6b75ed71ed14d09d7b42d6300013 > > > > > > > > Ah, ok, thanks for the pointer! > > > > > > > > I'm a little uneasy here, still. > > > > > > > > By backporting this we're also backporting the new breakage of the stack > > > > unwinder, and the minimal change for backports would be to add the lock and not > > > > the new stack (which was added for additinoal robustness, not to fix the bug > > > > the lock fixes). > > > > > > > > I do appreciate that the additional stack is likely more useful than the > > > > occasional diagnostic output from the kernel, but it does seem like this has > > > > traded off one bug for another, and I'm just a little annoyed because I pointed > > > > that out before the first pull request was made. > > > > > > > > I do know that this isn't malicious, and I'm not trying to start a fight, but > > > > now we have to consider whether we want/need to backport a stack unwinder fix > > > > to account for this, and we hadn't had that discussion before. > > > > > > > > > > In that case, let's drop these backports for the time being, and > > > collaborate on a solution that works for all of us. > > > > > > Greg, could you please drop these again? Thanks. > > > > Dropped now from all queues, thanks. > > Now in Mainline as: > > 18bba1843fc7f efi: rt-wrapper: Add missing include > ff7a167961d1b arm64: efi: Execute runtime services from a dedicated stack > > Would you be kind enough to re-collect them please? Now queued up for 5.10.y and newer. greg k-h