From: Mikulas Patocka <mpatocka@redhat.com> stable inclusion from linux-4.19.133 commit 35a9af8ddb6271fb20b9f4fa07c26fec1e6c52df Bugzilla: 38833 -------------------------------- commit 6958c1c640af8c3f40fa8a2eee3b5b905d95b677 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> --- 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 e803809409b8..b5c57344bc2f 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> @@ -2863,17 +2864,25 @@ 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) -- 2.25.1