dm: use noio when sending kobject event (6958c1c6) · Commits · 戴 / test

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>

drivers/md/dm.c

+12 −3

Original line number	Diff line number	Diff line
		@@ -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,
		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)

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