From 6958c1c640af8c3f40fa8a2eee3b5b905d95b677 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 8 Jul 2020 12:25:20 -0400
Subject: [PATCH] dm: use noio when sending kobject event
Git-commit: 6958c1c640af8c3f40fa8a2eee3b5b905d95b677
Patch-mainline: v5.8-rc5
References: bsc#1177529
kobject_uevent may allocate memory and it may be called while there are dm
devices suspended. The allocation may recurse into a suspended device,
causing a deadlock. We must set the noio flag when sending a uevent.
The observed deadlock was reported here:
https://www.redhat.com/archives/dm-devel/2020-March/msg00025.html
Reported-by: Khazhismel Kumykov <khazhy@google.com>
Reported-by: Tahsin Erdogan <tahsin@google.com>
Reported-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Coly Li <colyli@suse.de>
---
drivers/md/dm.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4cc7e2599664..52449afd58eb 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -12,6 +12,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/blkpg.h>
#include <linux/bio.h>
@@ -2939,17 +2940,25 @@ EXPORT_SYMBOL_GPL(dm_internal_resume_fast);
int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
unsigned cookie)
{
+ int r;
+ unsigned noio_flag;
char udev_cookie[DM_COOKIE_LENGTH];
char *envp[] = { udev_cookie, NULL };
+ noio_flag = memalloc_noio_save();
+
if (!cookie)
- return kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
+ r = kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
else {
snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
DM_COOKIE_ENV_VAR_NAME, cookie);
- return kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
- action, envp);
+ r = kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
+ action, envp);
}
+
+ memalloc_noio_restore(noio_flag);
+
+ return r;
}
uint32_t dm_next_uevent_seq(struct mapped_device *md)
--
2.26.2