The patch titled Subject: x86/mce: add EX_TYPE_EFAULT_REG as in-kernel recovery context to fix copy-from-user operations regression has been added to the -mm mm-unstable branch. Its filename is x86-mce-add-ex_type_efault_reg-as-in-kernel-recovery-context-to-fix-copy-from-user-operations-regression.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Shuai Xue xueshuai@linux.alibaba.com Subject: x86/mce: add EX_TYPE_EFAULT_REG as in-kernel recovery context to fix copy-from-user operations regression Date: Mon, 17 Feb 2025 14:33:33 +0800

Commit 4c132d1d844a ("x86/futex: Remove .fixup usage") introduced a new extable fixup type, EX_TYPE_EFAULT_REG, and later patches updated the extable fixup type for copy-from-user operations, changing it from EX_TYPE_UACCESS to EX_TYPE_EFAULT_REG.

Specifically, commit 99641e094d6c ("x86/uaccess: Remove .fixup usage") altered the extable fixup type for the get_user family, while commit 4c132d1d844a ("x86/futex: Remove .fixup usage") addressed the futex operations. This change inadvertently caused a regression where the error context for some copy-from-user operations no longer functions as an in-kernel recovery context, leading to kernel panics with the message: "Machine check: Data load in unrecoverable area of kernel."

To fix the regression, add EX_TYPE_EFAULT_REG as a in-kernel recovery context for copy-from-user operations.

Link: https://lkml.kernel.org/r/20250217063335.22257-4-xueshuai@linux.alibaba.com Signed-off-by: Shuai Xue xueshuai@linux.alibaba.com Fixes: 4c132d1d844a ("x86/futex: Remove .fixup usage") Cc: stable@vger.kernel.org Cc: Acked-by:Thomas Gleixner tglx@linutronix.de Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: Borislav Betkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: Jane Chu jane.chu@oracle.com Cc: Jarkko Sakkinen jarkko@kernel.org Cc: Jonathan Cameron Jonathan.Cameron@huawei.com Cc: Josh Poimboeuf jpoimboe@kernel.org Cc: linmiaohe linmiaohe@huawei.com Cc: "Luck, Tony" tony.luck@intel.com Cc: Naoya Horiguchi nao.horiguchi@gmail.com Cc: Peter Zijlstra peterz@infradead.org Cc: Ruidong Tian tianruidong@linux.alibaba.com Cc: Yazen Ghannam yazen.ghannam@amd.com Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

arch/x86/kernel/cpu/mce/severity.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/cpu/mce/severity.c~x86-mce-add-ex_type_efault_reg-as-in-kernel-recovery-context-to-fix-copy-from-user-operations-regression +++ a/arch/x86/kernel/cpu/mce/severity.c @@ -16,6 +16,7 @@ #include <asm/traps.h> #include <asm/insn.h> #include <asm/insn-eval.h> +#include <linux/extable.h>

#include "internal.h"

@@ -285,7 +286,8 @@ static bool is_copy_from_user(struct pt_ */ static noinstr int error_context(struct mce *m, struct pt_regs *regs) { - int fixup_type; + const struct exception_table_entry *e; + int fixup_type, imm; bool copy_user;

if ((m->cs & 3) == 3) @@ -294,9 +296,14 @@ static noinstr int error_context(struct if (!mc_recoverable(m->mcgstatus)) return IN_KERNEL;

+ e = search_exception_tables(m->ip); + if (!e) + return IN_KERNEL; + /* Allow instrumentation around external facilities usage. */ instrumentation_begin(); - fixup_type = ex_get_fixup_type(m->ip); + fixup_type = FIELD_GET(EX_DATA_TYPE_MASK, e->data); + imm = FIELD_GET(EX_DATA_IMM_MASK, e->data); copy_user = is_copy_from_user(regs); instrumentation_end();

@@ -304,9 +311,13 @@ static noinstr int error_context(struct case EX_TYPE_UACCESS: if (!copy_user) return IN_KERNEL; - m->kflags |= MCE_IN_KERNEL_COPYIN; - fallthrough; - + m->kflags |= MCE_IN_KERNEL_COPYIN | MCE_IN_KERNEL_RECOV; + return IN_KERNEL_RECOV; + case EX_TYPE_IMM_REG: + if (!copy_user || imm != -EFAULT) + return IN_KERNEL; + m->kflags |= MCE_IN_KERNEL_COPYIN | MCE_IN_KERNEL_RECOV; + return IN_KERNEL_RECOV; case EX_TYPE_FAULT_MCE_SAFE: case EX_TYPE_DEFAULT_MCE_SAFE: m->kflags |= MCE_IN_KERNEL_RECOV; _

Patches currently in -mm which might be from xueshuai@linux.alibaba.com are

x86-mce-collect-error-message-for-severities-below-mce_panic_severity.patch x86-mce-dump-error-msg-from-severities.patch x86-mce-add-ex_type_efault_reg-as-in-kernel-recovery-context-to-fix-copy-from-user-operations-regression.patch mm-hwpoison-fix-incorrect-not-recovered-report-for-recovered-clean-pages.patch mm-memory-failure-move-return-value-documentation-to-function-declaration.patch