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Message-ID: <87frrii66q.fsf@mail.lhotse>
Date: Tue, 06 Aug 2024 15:14:21 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Jinjie Ruan <ruanjinjie@...wei.com>, dennis@...nel.org, tj@...nel.org,
cl@...ux.com, benh@...nel.crashing.org, paulus@...ba.org,
christophe.leroy@...roup.eu, mahesh@...ux.ibm.com,
gregkh@...uxfoundation.org, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org
Cc: ruanjinjie@...wei.com
Subject: Re: [PATCH v5.10] powerpc: Avoid nmi_enter/nmi_exit in real mode
interrupt.
Hi Jinjie Ruan,
If you want to submit this as a stable backport you need to send it
To: stable@...r.kernel.org.
Jinjie Ruan <ruanjinjie@...wei.com> writes:
> From: Mahesh Salgaonkar <mahesh@...ux.ibm.com>
Although it's somewhat modified, this is still a backport of an upstream
commit, so it should include the following line:
[ Upstream commit 0db880fc865ffb522141ced4bfa66c12ab1fbb70 ]
> nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
> crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
> interrupt handler) if percpu allocation comes from vmalloc area.
>
> Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
> wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
> percpu allocation is from the embedded first chunk. However with
> CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
> allocation can come from the vmalloc area.
>
> With kernel command line "percpu_alloc=page" we can force percpu allocation
> to come from vmalloc area and can see kernel crash in machine_check_early:
>
> [ 1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
> [ 1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
> [ 1.215719] --- interrupt: 200
> [ 1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
> [ 1.215722] [c000000fffd731b0] [0000000000000000] 0x0
> [ 1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8
>
> Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
> first chunk is not embedded.
>
> CVE-2024-42126
> Cc: stable@...r.kernel.org
> Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Tested-by: Shirisha Ganta <shirisha@...ux.ibm.com>
> Signed-off-by: Mahesh Salgaonkar <mahesh@...ux.ibm.com>
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> Link: https://msgid.link/20240410043006.81577-1-mahesh@linux.ibm.com
> [ Conflicts in arch/powerpc/include/asm/interrupt.h
> because machine_check_early() has been refactored. ]
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
> arch/powerpc/include/asm/percpu.h | 10 ++++++++++
> arch/powerpc/kernel/mce.c | 14 +++++++++++---
> arch/powerpc/kernel/setup_64.c | 2 ++
> 3 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
> index 8e5b7d0b851c..634970ce13c6 100644
> --- a/arch/powerpc/include/asm/percpu.h
> +++ b/arch/powerpc/include/asm/percpu.h
> @@ -15,6 +15,16 @@
> #endif /* CONFIG_SMP */
> #endif /* __powerpc64__ */
>
> +#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && defined(CONFIG_SMP)
> +#include <linux/jump_label.h>
> +DECLARE_STATIC_KEY_FALSE(__percpu_first_chunk_is_paged);
> +
> +#define percpu_first_chunk_is_paged \
> + (static_key_enabled(&__percpu_first_chunk_is_paged.key))
> +#else
> +#define percpu_first_chunk_is_paged false
> +#endif /* CONFIG_PPC64 && CONFIG_SMP */
> +
> #include <asm-generic/percpu.h>
>
> #include <asm/paca.h>
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index 63702c0badb9..259343040e1b 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -594,8 +594,15 @@ long notrace machine_check_early(struct pt_regs *regs)
> u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
>
> this_cpu_set_ftrace_enabled(0);
> - /* Do not use nmi_enter/exit for pseries hpte guest */
> - if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
> + /*
> + * Do not use nmi_enter/exit for pseries hpte guest
> + *
> + * Likewise, do not use it in real mode if percpu first chunk is not
> + * embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
> + * are chances where percpu allocation can come from vmalloc area.
> + */
> + if ((radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR)) &&
> + !percpu_first_chunk_is_paged)
> nmi_enter();
>
> hv_nmi_check_nonrecoverable(regs);
> @@ -606,7 +613,8 @@ long notrace machine_check_early(struct pt_regs *regs)
> if (ppc_md.machine_check_early)
> handled = ppc_md.machine_check_early(regs);
>
> - if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
> + if ((radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR)) &&
> + !percpu_first_chunk_is_paged)
> nmi_exit();
>
> this_cpu_set_ftrace_enabled(ftrace_enabled);
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 3f8426bccd16..899d87de0165 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -824,6 +824,7 @@ static int pcpu_cpu_distance(unsigned int from, unsigned int to)
>
> unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
> EXPORT_SYMBOL(__per_cpu_offset);
> +DEFINE_STATIC_KEY_FALSE(__percpu_first_chunk_is_paged);
>
> static void __init pcpu_populate_pte(unsigned long addr)
> {
> @@ -903,6 +904,7 @@ void __init setup_per_cpu_areas(void)
> if (rc < 0)
> panic("cannot initialize percpu area (err=%d)", rc);
>
> + static_key_enable(&__percpu_first_chunk_is_paged.key);
> delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
> for_each_possible_cpu(cpu) {
> __per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
This looks reasonable to me, though I haven't tested it, I assume you
have done so.
Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
cheers
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