The patch titled
Subject: x86/traps: avoid KMSAN bugs originating from handle_bug()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
x86-traps-avoid-kmsan-bugs-originating-from-handle_bug.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-traps-avoid-kmsan-bugs-originating-from-handle_bug.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: x86/traps: avoid KMSAN bugs originating from handle_bug()
Date: Wed, 2 Nov 2022 12:06:11 +0100
There is a case in exc_invalid_op handler that is executed outside the
irqentry_enter()/irqentry_exit() region when an UD2 instruction is used to
encode a call to __warn().
In that case the `struct pt_regs` passed to the interrupt handler is never
unpoisoned by KMSAN (this is normally done in irqentry_enter()), which
leads to false positives inside handle_bug().
Use kmsan_unpoison_entry_regs() to explicitly unpoison those registers
before using them.
Link: https://lkml.kernel.org/r/20221102110611.1085175-5-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/traps.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/x86/kernel/traps.c~x86-traps-avoid-kmsan-bugs-originating-from-handle_bug
+++ a/arch/x86/kernel/traps.c
@@ -15,6 +15,7 @@
#include <linux/context_tracking.h>
#include <linux/interrupt.h>
#include <linux/kallsyms.h>
+#include <linux/kmsan.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
@@ -301,6 +302,12 @@ static noinstr bool handle_bug(struct pt
{
bool handled = false;
+ /*
+ * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug()
+ * is a rare case that uses @regs without passing them to
+ * irqentry_enter().
+ */
+ kmsan_unpoison_entry_regs(regs);
if (!is_valid_bugaddr(regs->ip))
return handled;
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
kmsan-core-kmsan_in_runtime-should-return-true-in-nmi-context.patch
x86-uaccess-instrument-copy_from_user_nmi.patch
kconfigdebug-ensure-early-check-for-kmsan-in-config_kmsan_warn.patch
kmsan-make-sure-preempt_rt-is-off.patch
x86-traps-avoid-kmsan-bugs-originating-from-handle_bug.patch
