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Message-ID: <CALTww29QY49_DA3e71fev+YDCQ-Qse5tGVCdjY+czw096K0EAg@mail.gmail.com>
Date: Tue, 4 Nov 2025 09:24:56 +0800
From: Xiao Ni <xni@...hat.com>
To: linan666@...weicloud.com
Cc: corbet@....net, song@...nel.org, yukuai@...as.com, linan122@...wei.com,
hare@...e.de, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-raid@...r.kernel.org, yangerkun@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH v9 2/5] md: init bioset in mddev_init
On Mon, Nov 3, 2025 at 9:06 PM <linan666@...weicloud.com> wrote:
>
> From: Li Nan <linan122@...wei.com>
>
> IO operations may be needed before md_run(), such as updating metadata
> after writing sysfs. Without bioset, this triggers a NULL pointer
> dereference as below:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000020
> Call Trace:
> md_update_sb+0x658/0xe00
> new_level_store+0xc5/0x120
> md_attr_store+0xc9/0x1e0
> sysfs_kf_write+0x6f/0xa0
> kernfs_fop_write_iter+0x141/0x2a0
> vfs_write+0x1fc/0x5a0
> ksys_write+0x79/0x180
> __x64_sys_write+0x1d/0x30
> x64_sys_call+0x2818/0x2880
> do_syscall_64+0xa9/0x580
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
>
> Reproducer
> ```
> mdadm -CR /dev/md0 -l1 -n2 /dev/sd[cd]
> echo inactive > /sys/block/md0/md/array_state
> echo 10 > /sys/block/md0/md/new_level
> ```
>
> mddev_init() can only be called once per mddev, no need to test if bioset
> has been initialized anymore.
>
> Fixes: d981ed841930 ("md: Add new_level sysfs interface")
> Signed-off-by: Li Nan <linan122@...wei.com>
> ---
> drivers/md/md.c | 69 +++++++++++++++++++++++--------------------------
> 1 file changed, 33 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index f6fd55a1637b..dffc6a482181 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -730,6 +730,8 @@ static void mddev_clear_bitmap_ops(struct mddev *mddev)
>
> int mddev_init(struct mddev *mddev)
> {
> + int err = 0;
> +
> if (!IS_ENABLED(CONFIG_MD_BITMAP))
> mddev->bitmap_id = ID_BITMAP_NONE;
> else
> @@ -741,10 +743,23 @@ int mddev_init(struct mddev *mddev)
>
> if (percpu_ref_init(&mddev->writes_pending, no_op,
> PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
> - percpu_ref_exit(&mddev->active_io);
> - return -ENOMEM;
> + err = -ENOMEM;
> + goto exit_acitve_io;
> }
>
> + err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
> + if (err)
> + goto exit_writes_pending;
> +
> + err = bioset_init(&mddev->sync_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
> + if (err)
> + goto exit_bio_set;
> +
> + err = bioset_init(&mddev->io_clone_set, BIO_POOL_SIZE,
> + offsetof(struct md_io_clone, bio_clone), 0);
> + if (err)
> + goto exit_sync_set;
> +
> /* We want to start with the refcount at zero */
> percpu_ref_put(&mddev->writes_pending);
>
> @@ -773,11 +788,24 @@ int mddev_init(struct mddev *mddev)
> INIT_WORK(&mddev->del_work, mddev_delayed_delete);
>
> return 0;
> +
> +exit_sync_set:
> + bioset_exit(&mddev->sync_set);
> +exit_bio_set:
> + bioset_exit(&mddev->bio_set);
> +exit_writes_pending:
> + percpu_ref_exit(&mddev->writes_pending);
> +exit_acitve_io:
> + percpu_ref_exit(&mddev->active_io);
> + return err;
> }
> EXPORT_SYMBOL_GPL(mddev_init);
>
> void mddev_destroy(struct mddev *mddev)
> {
> + bioset_exit(&mddev->bio_set);
> + bioset_exit(&mddev->sync_set);
> + bioset_exit(&mddev->io_clone_set);
> percpu_ref_exit(&mddev->active_io);
> percpu_ref_exit(&mddev->writes_pending);
> }
> @@ -6393,29 +6421,9 @@ int md_run(struct mddev *mddev)
> nowait = nowait && bdev_nowait(rdev->bdev);
> }
>
> - if (!bioset_initialized(&mddev->bio_set)) {
> - err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
> - if (err)
> - return err;
> - }
> - if (!bioset_initialized(&mddev->sync_set)) {
> - err = bioset_init(&mddev->sync_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
> - if (err)
> - goto exit_bio_set;
> - }
> -
> - if (!bioset_initialized(&mddev->io_clone_set)) {
> - err = bioset_init(&mddev->io_clone_set, BIO_POOL_SIZE,
> - offsetof(struct md_io_clone, bio_clone), 0);
> - if (err)
> - goto exit_sync_set;
> - }
> -
> pers = get_pers(mddev->level, mddev->clevel);
> - if (!pers) {
> - err = -EINVAL;
> - goto abort;
> - }
> + if (!pers)
> + return -EINVAL;
> if (mddev->level != pers->head.id) {
> mddev->level = pers->head.id;
> mddev->new_level = pers->head.id;
> @@ -6426,8 +6434,7 @@ int md_run(struct mddev *mddev)
> pers->start_reshape == NULL) {
> /* This personality cannot handle reshaping... */
> put_pers(pers);
> - err = -EINVAL;
> - goto abort;
> + return -EINVAL;
> }
>
> if (pers->sync_request) {
> @@ -6554,12 +6561,6 @@ int md_run(struct mddev *mddev)
> mddev->private = NULL;
> put_pers(pers);
> md_bitmap_destroy(mddev);
> -abort:
> - bioset_exit(&mddev->io_clone_set);
> -exit_sync_set:
> - bioset_exit(&mddev->sync_set);
> -exit_bio_set:
> - bioset_exit(&mddev->bio_set);
> return err;
> }
> EXPORT_SYMBOL_GPL(md_run);
> @@ -6784,10 +6785,6 @@ static void __md_stop(struct mddev *mddev)
> mddev->private = NULL;
> put_pers(pers);
> clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> -
> - bioset_exit(&mddev->bio_set);
> - bioset_exit(&mddev->sync_set);
> - bioset_exit(&mddev->io_clone_set);
> }
>
> void md_stop(struct mddev *mddev)
> --
> 2.39.2
>
Looks good to me.
Reviewed-by: Xiao Ni <xni@...hat.com>
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