Re: [PATCH] ubi: block: fix null-pointer-dereference in ubiblock_create()

[Li Nan]

在 2024/4/28 15:51, Zhihao Cheng 写道:
> 在 2024/4/28 15:19, linan666@xxxxxxxxxxxxxxx 写道:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > Similar to commit adbf4c4954e3 ("ubi: block: fix memleak in
> > ubiblock_create()"), 'dev->gd' is not assigned but dereferenced if
> > blk_mq_alloc_tag_set() fails, and leading to a null-pointer-dereference.
> >
> > Using 'gd' directly here is not a good idea, too. 'gd->part0.bd_device'
> > is not initialized at this point. The error log will be:
> >    block (null): block: dynamic minor allocation failed
> >
> > Fix it by using pr_err() and print ubi id.
> >
> > Fixes: 77567b25ab9f ("ubi: use blk_mq_alloc_disk and blk_cleanup_disk")
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >   drivers/mtd/ubi/block.c | 7 ++++---
> >   1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
> > index f82e3423acb9..bf7308e8ec2f 100644
> > --- a/drivers/mtd/ubi/block.c
> > +++ b/drivers/mtd/ubi/block.c
> > @@ -390,7 +390,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
> >       ret = blk_mq_alloc_tag_set(&dev->tag_set);
> >       if (ret) {
> > -        dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
> > +        pr_err("ubiblock%d_%d: blk_mq_alloc_tag_set failed\n",
> > +            dev->ubi_num, dev->vol_id);
> >           goto out_free_dev;
> >       }
> > @@ -407,8 +408,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
> >       gd->minors = 1;
> >       gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, 
> > GFP_KERNEL);
>
> There is no need to modify this place. The device of 'gd' is initialized in 
> blk_mq_alloc_disk. Refer to nbd_dev_add.


The print of this dev_err() is:
  block (null): block: dynamic minor allocation failed
	~~~~~~
There is no information about which device failed. dev_err()
use 'kobject_name(&dev->kobj)' here, which is init in device_add_disk()
later. So use pr_err() here can print more detail.

I will split the patch into two in v2 to make it clearer.

> >       if (gd->first_minor < 0) {
> > -        dev_err(disk_to_dev(gd),
> > -            "block: dynamic minor allocation failed");
> > +        pr_err("ubiblock%d_%d: block: dynamic minor allocation failed\n",
> > +            dev->ubi_num, dev->vol_id);
> >           ret = -ENODEV;
> >           goto out_cleanup_disk;
> >       }

--
Thanks,
Nan