From 3e453522593d74a87cf68a38e14aa36ebca1dbcd Mon Sep 17 00:00:00 2001 From: Xiao Ni Date: Wed, 22 Feb 2023 11:59:16 +0800 Subject: [PATCH] md: Free resources in __md_stop If md_run() fails after ->active_io is initialized, then percpu_ref_exit is called in error path. However, later md_free_disk will call percpu_ref_exit again which leads to a panic because of null pointer dereference. It can also trigger this bug when resources are initialized but are freed in error path, then will be freed again in md_free_disk. BUG: kernel NULL pointer dereference, address: 0000000000000038 Oops: 0000 [#1] PREEMPT SMP Workqueue: md_misc mddev_delayed_delete RIP: 0010:free_percpu+0x110/0x630 Call Trace: __percpu_ref_exit+0x44/0x70 percpu_ref_exit+0x16/0x90 md_free_disk+0x2f/0x80 disk_release+0x101/0x180 device_release+0x84/0x110 kobject_put+0x12a/0x380 kobject_put+0x160/0x380 mddev_delayed_delete+0x19/0x30 process_one_work+0x269/0x680 worker_thread+0x266/0x640 kthread+0x151/0x1b0 ret_from_fork+0x1f/0x30 For creating raid device, md raid calls do_md_run->md_run, dm raid calls md_run. We alloc those memory in md_run. For stopping raid device, md raid calls do_md_stop->__md_stop, dm raid calls md_stop->__md_stop. So we can free those memory resources in __md_stop. Fixes: 72adae23a72c ("md: Change active_io to percpu") Reported-and-tested-by: Yu Kuai Signed-off-by: Xiao Ni Signed-off-by: Song Liu --- drivers/md/md.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 927a43db5dfbb9..f5480778e2f7c8 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6256,6 +6256,11 @@ static void __md_stop(struct mddev *mddev) mddev->to_remove = &md_redundancy_group; module_put(pers->owner); clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); + + percpu_ref_exit(&mddev->writes_pending); + percpu_ref_exit(&mddev->active_io); + bioset_exit(&mddev->bio_set); + bioset_exit(&mddev->sync_set); } void md_stop(struct mddev *mddev) @@ -6265,10 +6270,6 @@ void md_stop(struct mddev *mddev) */ __md_stop_writes(mddev); __md_stop(mddev); - percpu_ref_exit(&mddev->writes_pending); - percpu_ref_exit(&mddev->active_io); - bioset_exit(&mddev->bio_set); - bioset_exit(&mddev->sync_set); } EXPORT_SYMBOL_GPL(md_stop); @@ -7839,11 +7840,6 @@ static void md_free_disk(struct gendisk *disk) { struct mddev *mddev = disk->private_data; - percpu_ref_exit(&mddev->writes_pending); - percpu_ref_exit(&mddev->active_io); - bioset_exit(&mddev->bio_set); - bioset_exit(&mddev->sync_set); - mddev_free(mddev); }