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Message-ID: <20240813113705.1837673-1-ruanjinjie@huawei.com>
Date: Tue, 13 Aug 2024 11:37:05 +0000
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <dennis@...nel.org>, <tj@...nel.org>, <cl@...ux.com>,
<mpe@...erman.id.au>, <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>, <stable@...r.kernel.org>
CC: <ruanjinjie@...wei.com>
Subject: [PATCH v5.15 RESEND] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.
From: Mahesh Salgaonkar <mahesh@...ux.ibm.com>
[ 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#5.15.x
Cc: gregkh@...uxfoundation.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 interrupt_nmi_enter_prepare() and interrupt_nmi_exit_prepare()
has been refactored. ]
Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
---
arch/powerpc/include/asm/interrupt.h | 14 ++++++++++----
arch/powerpc/include/asm/percpu.h | 10 ++++++++++
arch/powerpc/kernel/setup_64.c | 2 ++
3 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index e592e65e7665..49285b147afe 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -285,18 +285,24 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
/*
* Do not use nmi_enter() for pseries hash guest taking a real-mode
* NMI because not everything it touches is within the RMA limit.
+ *
+ * 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 (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
+ if ((!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
!firmware_has_feature(FW_FEATURE_LPAR) ||
- radix_enabled() || (mfmsr() & MSR_DR))
+ radix_enabled() || (mfmsr() & MSR_DR)) &&
+ !percpu_first_chunk_is_paged)
nmi_enter();
}
static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
{
- if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
+ if ((!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
!firmware_has_feature(FW_FEATURE_LPAR) ||
- radix_enabled() || (mfmsr() & MSR_DR))
+ radix_enabled() || (mfmsr() & MSR_DR)) &&
+ !percpu_first_chunk_is_paged)
nmi_exit();
/*
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/setup_64.c b/arch/powerpc/kernel/setup_64.c
index eaa79a0996d1..37d5683ab298 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -825,6 +825,7 @@ 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)
{
@@ -904,6 +905,7 @@ 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];
--
2.34.1
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