Re: [PATCH v7 2/4] md: init bioset in mddev_init

[Li Nan]

在 2025/10/28 20:01, Yu Kuai 写道:
> Hi,
>
> 在 2025/10/27 15:29, linan122@xxxxxxxxxx 写道:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > 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
> > ```
> >
> > Fixes: d981ed841930 ("md: Add new_level sysfs interface")
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >    drivers/md/md.c | 74 +++++++++++++++++++++++++------------------------
> >    1 file changed, 38 insertions(+), 36 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index f6fd55a1637b..51f0201e4906 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
> > @@ -741,8 +743,26 @@ 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;
> > +	}
> > +
> > +	if (!bioset_initialized(&mddev->bio_set)) {
> > +		err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
>
> mddev_init() can only be called once for one mddev, no need to test if bioset
> is initialized here.

I will fix it in next version. Thanks for your review.

> > +		if (err)
> > +			goto exit_writes_pending;
> > +	}
> > +	if (!bioset_initialized(&mddev->sync_set)) {
>
> same here.

--
Thanks,
Nan