merged.
Bruce
In message: [linux-yocto][v6.6/standard/x86][PATCH] efi/unaccepted: touch soft
lockup during memory accept
on 13/06/2024 Bin Lan via lists.yoctoproject.org wrote:
> From: Chen Yu <yu.c.c...@intel.com>
>
> Commit 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by
> parallel memory acceptance") has released the spinlock so other CPUs can
> do memory acceptance in parallel and not triggers softlockup on other
> CPUs.
>
> However the softlock up was intermittent shown up if the memory of the
> TD guest is large, and the timeout of softlockup is set to 1 second:
>
> RIP: 0010:_raw_spin_unlock_irqrestore
> Call Trace:
> ? __hrtimer_run_queues
> <IRQ>
> ? hrtimer_interrupt
> ? watchdog_timer_fn
> ? __sysvec_apic_timer_interrupt
> ? __pfx_watchdog_timer_fn
> ? sysvec_apic_timer_interrupt
> </IRQ>
> ? __hrtimer_run_queues
> <TASK>
> ? hrtimer_interrupt
> ? asm_sysvec_apic_timer_interrupt
> ? _raw_spin_unlock_irqrestore
> ? __sysvec_apic_timer_interrupt
> ? sysvec_apic_timer_interrupt
> accept_memory
> try_to_accept_memory
> do_huge_pmd_anonymous_page
> get_page_from_freelist
> __handle_mm_fault
> __alloc_pages
> __folio_alloc
> ? __tdx_hypercall
> handle_mm_fault
> vma_alloc_folio
> do_user_addr_fault
> do_huge_pmd_anonymous_page
> exc_page_fault
> ? __do_huge_pmd_anonymous_page
> asm_exc_page_fault
> __handle_mm_fault
>
> When the local irq is enabled at the end of accept_memory(), the
> softlockup detects that the watchdog on single CPU has not been fed for
> a while. That is to say, even other CPUs will not be blocked by
> spinlock, the current CPU might be stunk with local irq disabled for a
> while, which hurts not only nmi watchdog but also softlockup.
>
> Chao Gao pointed out that the memory accept could be time costly and
> there was similar report before. Thus to avoid any softlocup detection
> during this stage, give the softlockup a flag to skip the timeout check
> at the end of accept_memory(), by invoking touch_softlockup_watchdog().
>
> This patch fixes CVE-2024-36936.
>
> Reported-by: Hossain, Md Iqbal <md.iqbal.hoss...@intel.com>
> Signed-off-by: Chen Yu <yu.c.c...@intel.com>
> Reviewed-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
> Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel
> memory acceptance")
> Signed-off-by: Ard Biesheuvel <a...@kernel.org>
> (cherry picked from commit 1c5a1627f48105cbab81d25ec2f72232bfaa8185)
> Signed-off-by: Bin Lan <bin.lan...@windriver.com>
> ---
> drivers/firmware/efi/unaccepted_memory.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/firmware/efi/unaccepted_memory.c
> b/drivers/firmware/efi/unaccepted_memory.c
> index 79fb687bb90f..30a831cc205c 100644
> --- a/drivers/firmware/efi/unaccepted_memory.c
> +++ b/drivers/firmware/efi/unaccepted_memory.c
> @@ -3,6 +3,8 @@
> #include <linux/efi.h>
> #include <linux/memblock.h>
> #include <linux/spinlock.h>
> +#include <linux/crash_dump.h>
> +#include <linux/nmi.h>
> #include <asm/unaccepted_memory.h>
>
> /* Protects unaccepted memory bitmap and accepting_list */
> @@ -148,6 +150,9 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
> }
>
> list_del(&range.list);
> +
> + touch_softlockup_watchdog();
> +
> spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
> }
>
> --
> 2.34.1
>
>
>
>
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