Re: [PATCH] md: fix null-ptr-deference in md_free_disk()
From: Xiao Ni <hidden>
Date: 2023-02-22 00:43:05
Also in:
lkml
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
Sorry, the patch was missed in the last email.
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 927a43db5dfb..f5480778e2f7 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); }
If we release those memories in md_free_disk, it's hard to find the corresponding relationship between alloc memory and free memory. If we free memory in __md_stop, it's easy to find the right place where those memories are free. Best Regards Xiao On Wed, Feb 22, 2023 at 8:39 AM Xiao Ni [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Hi Yu Kuai Thanks for reporting this problem. 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 how about this patch:diff --git a/drivers/md/md.c b/drivers/md/md.c index 927a43db5dfb..f5480778e2f7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.cOn Tue, Feb 21, 2023 at 9:33 PM Yu Kuai [off-list ref] wrote:quoted
From: Yu Kuai <redacted> If md_run() failed after 'acitive_io' is initialized, then percpu_ref_exit() is called in error path, however, later md_free_disk() will call percpu_ref_exit() again, which lead to following null-ptr-deference: BUG: kernel NULL pointer dereference, address: 0000000000000038 Oops: 0000 [#1] PREEMPT SMP CPU: 41 PID: 585 Comm: kworker/41:1 Not tainted 6.2.0-rc8-next-20230220 #1452 Workqueue: md_misc mddev_delayed_delete RIP: 0010:free_percpu+0x110/0x630 Call Trace: <TASK> __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 Since freeing mddev will exit 'active_io' unconditionally, fix the problem by removing exiting 'active_io' from error path, this way it will be delayed to free mddev. Fixes: 72adae23a72c ("md: Change active_io to percpu") Signed-off-by: Yu Kuai <redacted> --- drivers/md/md.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)diff --git a/drivers/md/md.c b/drivers/md/md.c index 927a43db5dfb..77124679b3fd 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c@@ -5851,7 +5851,7 @@ int md_run(struct mddev *mddev) if (!bioset_initialized(&mddev->bio_set)) { err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS); if (err) - goto exit_active_io; + return err; } if (!bioset_initialized(&mddev->sync_set)) { err = bioset_init(&mddev->sync_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);@@ -6039,8 +6039,6 @@ int md_run(struct mddev *mddev) bioset_exit(&mddev->sync_set); exit_bio_set: bioset_exit(&mddev->bio_set); -exit_active_io: - percpu_ref_exit(&mddev->active_io); return err; } EXPORT_SYMBOL_GPL(md_run); --2.31.1