From d2635f2012a44e3d469ab9a4022162dbe0e53f21 Mon Sep 17 00:00:00 2001
From: Christophe Leroy <christophe.leroy@csgroup.eu>
Date: Fri, 5 Nov 2021 13:40:40 -0700
Subject: [PATCH] mm: create a new system state and fix core_kernel_text()
core_kernel_text() considers that until system_state in at least
SYSTEM_RUNNING, init memory is valid.
But init memory is freed a few lines before setting SYSTEM_RUNNING, so
we have a small period of time when core_kernel_text() is wrong.
Create an intermediate system state called SYSTEM_FREEING_INIT that is
set before starting freeing init memory, and use it in
core_kernel_text() to report init memory invalid earlier.
Link: https://lkml.kernel.org/r/9ecfdee7dd4d741d172cb93ff1d87f1c58127c9a.1633001016.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/kernel.h | 1 +
init/main.c | 2 ++
kernel/extable.c | 2 +-
3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2776423a587e4..471bc05936796 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -248,6 +248,7 @@ extern bool early_boot_irqs_disabled;
extern enum system_states {
SYSTEM_BOOTING,
SYSTEM_SCHEDULING,
+ SYSTEM_FREEING_INITMEM,
SYSTEM_RUNNING,
SYSTEM_HALT,
SYSTEM_POWER_OFF,
diff --git a/init/main.c b/init/main.c
index 3c4054a955458..767ee26721760 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1506,6 +1506,8 @@ static int __ref kernel_init(void *unused)
kernel_init_freeable();
/* need to finish all async __init code before freeing the memory */
async_synchronize_full();
+
+ system_state = SYSTEM_FREEING_INITMEM;
kprobe_free_init_mem();
ftrace_free_init_mem();
kgdb_free_init_mem();
diff --git a/kernel/extable.c b/kernel/extable.c
index b0ea5eb0c3b43..290661f68e6b3 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -76,7 +76,7 @@ int notrace core_kernel_text(unsigned long addr)
addr < (unsigned long)_etext)
return 1;
- if (system_state < SYSTEM_RUNNING &&
+ if (system_state < SYSTEM_FREEING_INITMEM &&
init_kernel_text(addr))
return 1;
return 0;
--
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