+ x86-mce-add-ex_type_efault_reg-as-in-kernel-recovery-context-to-fix-copy-from-user-operations-regression.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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/x86-mce-add-ex_type_efault_reg-as-in-kernel-recovery-context-to-fix-copy-from-user-operations-regression.patch

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