[PATCH v3] block: fix incorrect references to disk objects

[PATCH v3] block: fix incorrect references to disk objects

[Zqiang]

When adding partitions to the disk, the reference count of the disk
object is increased. then alloc partition device and called
device_add(), if the device_add() return error, the reference
count of the disk object will be reduced twice, at put_device(pdev)
and put_disk(disk). this leads to the end of the object's life cycle
prematurely, and trigger following calltrace.

  __init_work+0x2d/0x50 kernel/workqueue.c:519
  synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
  bdi_remove_from_list mm/backing-dev.c:938 [inline]
  bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
  release_bdi+0xa1/0xc0 mm/backing-dev.c:968
  kref_put include/linux/kref.h:65 [inline]
  bdi_put+0x72/0xa0 mm/backing-dev.c:976
  bdev_free_inode+0x11e/0x220 block/bdev.c:408
  i_callback+0x3f/0x70 fs/inode.c:226
  rcu_do_batch kernel/rcu/tree.c:2508 [inline]
  rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
  __do_softirq+0x1d7/0x93b kernel/softirq.c:558
  invoke_softirq kernel/softirq.c:432 [inline]
  __irq_exit_rcu kernel/softirq.c:636 [inline]
  irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
  sysvec_apic_timer_interrupt+0x93/0xc0

Return directly after calling the put_device().

Reported-by: Hao Sun <sunhao.th@gmail.com>
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
---
 v1->v2:
 directly returning instead of assigning disk to NULL
 v2->v3:
 modify description information

 block/partitions/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index 9dbddc355b40..ed5deef1d7e1 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -424,6 +424,7 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 	device_del(pdev);
 out_put:
 	put_device(pdev);
+	return ERR_PTR(err);
 out_put_disk:
 	put_disk(disk);
 	return ERR_PTR(err);
-- 
2.17.1

Re: [PATCH v3] block: fix incorrect references to disk objects

[Matthew Wilcox]

On Mon, Oct 18, 2021 at 07:58:07PM +0800, Zqiang wrote:
> When adding partitions to the disk, the reference count of the disk
> object is increased. then alloc partition device and called
> device_add(), if the device_add() return error, the reference
> count of the disk object will be reduced twice, at put_device(pdev)
> and put_disk(disk). this leads to the end of the object's life cycle
> prematurely, and trigger following calltrace.
> 
>   __init_work+0x2d/0x50 kernel/workqueue.c:519
>   synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
>   bdi_remove_from_list mm/backing-dev.c:938 [inline]
>   bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
>   release_bdi+0xa1/0xc0 mm/backing-dev.c:968
>   kref_put include/linux/kref.h:65 [inline]
>   bdi_put+0x72/0xa0 mm/backing-dev.c:976
>   bdev_free_inode+0x11e/0x220 block/bdev.c:408
>   i_callback+0x3f/0x70 fs/inode.c:226
>   rcu_do_batch kernel/rcu/tree.c:2508 [inline]
>   rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
>   __do_softirq+0x1d7/0x93b kernel/softirq.c:558
>   invoke_softirq kernel/softirq.c:432 [inline]
>   __irq_exit_rcu kernel/softirq.c:636 [inline]
>   irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
>   sysvec_apic_timer_interrupt+0x93/0xc0
> 
> Return directly after calling the put_device().
> 
> Reported-by: Hao Sun <sunhao.th@gmail.com>
> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>

Fixes: 9d3b8813895d ("block: change the refcounting for partitions")
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Re: [PATCH v3] block: fix incorrect references to disk objects

[Zqiang]

On 2021/10/18 下午8:26, Matthew Wilcox wrote:
> On Mon, Oct 18, 2021 at 07:58:07PM +0800, Zqiang wrote:
>> When adding partitions to the disk, the reference count of the disk
>> object is increased. then alloc partition device and called
>> device_add(), if the device_add() return error, the reference
>> count of the disk object will be reduced twice, at put_device(pdev)
>> and put_disk(disk). this leads to the end of the object's life cycle
>> prematurely, and trigger following calltrace.
>>
>>    __init_work+0x2d/0x50 kernel/workqueue.c:519
>>    synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
>>    bdi_remove_from_list mm/backing-dev.c:938 [inline]
>>    bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
>>    release_bdi+0xa1/0xc0 mm/backing-dev.c:968
>>    kref_put include/linux/kref.h:65 [inline]
>>    bdi_put+0x72/0xa0 mm/backing-dev.c:976
>>    bdev_free_inode+0x11e/0x220 block/bdev.c:408
>>    i_callback+0x3f/0x70 fs/inode.c:226
>>    rcu_do_batch kernel/rcu/tree.c:2508 [inline]
>>    rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
>>    __do_softirq+0x1d7/0x93b kernel/softirq.c:558
>>    invoke_softirq kernel/softirq.c:432 [inline]
>>    __irq_exit_rcu kernel/softirq.c:636 [inline]
>>    irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
>>    sysvec_apic_timer_interrupt+0x93/0xc0
>>
>> Return directly after calling the put_device().
>>
>> Reported-by: Hao Sun <sunhao.th@gmail.com>
>> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
> Fixes: 9d3b8813895d ("block: change the refcounting for partitions")
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Hello Jens Axboe

The patch description information of the previous v2 version is 
incorrect, v3 modified the description information, please applied the 
v3 version.

Thanks

Zqiang

Re: [PATCH v3] block: fix incorrect references to disk objects

[Jens Axboe]

On 10/25/21 2:27 AM, Zqiang wrote:
> 
> On 2021/10/18 下午8:26, Matthew Wilcox wrote:
>> On Mon, Oct 18, 2021 at 07:58:07PM +0800, Zqiang wrote:
>>> When adding partitions to the disk, the reference count of the disk
>>> object is increased. then alloc partition device and called
>>> device_add(), if the device_add() return error, the reference
>>> count of the disk object will be reduced twice, at put_device(pdev)
>>> and put_disk(disk). this leads to the end of the object's life cycle
>>> prematurely, and trigger following calltrace.
>>>
>>>    __init_work+0x2d/0x50 kernel/workqueue.c:519
>>>    synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
>>>    bdi_remove_from_list mm/backing-dev.c:938 [inline]
>>>    bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
>>>    release_bdi+0xa1/0xc0 mm/backing-dev.c:968
>>>    kref_put include/linux/kref.h:65 [inline]
>>>    bdi_put+0x72/0xa0 mm/backing-dev.c:976
>>>    bdev_free_inode+0x11e/0x220 block/bdev.c:408
>>>    i_callback+0x3f/0x70 fs/inode.c:226
>>>    rcu_do_batch kernel/rcu/tree.c:2508 [inline]
>>>    rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
>>>    __do_softirq+0x1d7/0x93b kernel/softirq.c:558
>>>    invoke_softirq kernel/softirq.c:432 [inline]
>>>    __irq_exit_rcu kernel/softirq.c:636 [inline]
>>>    irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
>>>    sysvec_apic_timer_interrupt+0x93/0xc0
>>>
>>> Return directly after calling the put_device().
>>>
>>> Reported-by: Hao Sun <sunhao.th@gmail.com>
>>> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
>> Fixes: 9d3b8813895d ("block: change the refcounting for partitions")
>> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> Hello Jens Axboe
> 
> The patch description information of the previous v2 version is 
> incorrect, v3 modified the description information, please applied the 
> v3 version.

This patch is already upstream, I don't have a time machine...

-- 
Jens Axboe