2018-11-09 01:11:49

by Manjunath Patil

Subject: [PATCH v2] xen-blkfront: fix kernel panic with blkfront_remove()

When we try to detach the device, blkfront_remove() tries to access
blkfront_info leading to kernel panic.

Typical call stack involving panic -
#10 page_fault at ffffffff816f25df
[exception RIP: blkif_free+46]
#11 blkfront_remove at ffffffffa004de47 [xen_blkfront]
#12 xenbus_dev_remove at ffffffff813faa4c
#13 __device_release_driver at ffffffff814769aa
#14 device_release_driver at ffffffff81476a63
#15 bus_remove_device at ffffffff814762eb
#16 device_del at ffffffff81472684
#17 device_unregister at ffffffff814727e2
#18 xenbus_dev_changed at ffffffff813fa89f
#19 frontend_changed at ffffffff813fca19
#20 xenwatch_thread at ffffffff813f88f9
#21 kthread at ffffffff810a486b
#22 ret_from_fork at ffffffff816ed2a8

Cc: [email protected]
Signed-off-by: Manjunath Patil <[email protected]>
---
v2: style change. added the missing space b/w if and (
---
drivers/block/xen-blkfront.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index dc8fe25..2d8b10d 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2496,6 +2496,9 @@ static int blkfront_remove(struct xenbus_device *xbdev)

dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);

+ if (!info)
+ return 0;
+
blkif_free(info, 0);

mutex_lock(&info->mutex);
--
1.7.1

2018-11-09 06:17:03

by Juergen Gross

Subject: Re: [PATCH v2] xen-blkfront: fix kernel panic with blkfront_remove()

On 09/11/2018 02:10, Manjunath Patil wrote:
> When we try to detach the device, blkfront_remove() tries to access
> blkfront_info leading to kernel panic.
>
> Typical call stack involving panic -
> #10 page_fault at ffffffff816f25df
> [exception RIP: blkif_free+46]
> #11 blkfront_remove at ffffffffa004de47 [xen_blkfront]
> #12 xenbus_dev_remove at ffffffff813faa4c
> #13 __device_release_driver at ffffffff814769aa
> #14 device_release_driver at ffffffff81476a63
> #15 bus_remove_device at ffffffff814762eb
> #16 device_del at ffffffff81472684
> #17 device_unregister at ffffffff814727e2
> #18 xenbus_dev_changed at ffffffff813fa89f
> #19 frontend_changed at ffffffff813fca19
> #20 xenwatch_thread at ffffffff813f88f9
> #21 kthread at ffffffff810a486b
> #22 ret_from_fork at ffffffff816ed2a8
>
> Cc: [email protected]
> Signed-off-by: Manjunath Patil <[email protected]>

Commit f92898e7f32e3 already added that.


Juergen

2018-11-09 19:10:00

by Manjunath Patil

Subject: Re: [Xen-devel] [PATCH v2] xen-blkfront: fix kernel panic with blkfront_remove()

oops! sorry for not noticing this.

-Manjunath

On 11/8/2018 10:16 PM, Juergen Gross wrote:
> On 09/11/2018 02:10, Manjunath Patil wrote:
>> When we try to detach the device, blkfront_remove() tries to access
>> blkfront_info leading to kernel panic.
>>
>> Typical call stack involving panic -
>> #10 page_fault at ffffffff816f25df
>> [exception RIP: blkif_free+46]
>> #11 blkfront_remove at ffffffffa004de47 [xen_blkfront]
>> #12 xenbus_dev_remove at ffffffff813faa4c
>> #13 __device_release_driver at ffffffff814769aa
>> #14 device_release_driver at ffffffff81476a63
>> #15 bus_remove_device at ffffffff814762eb
>> #16 device_del at ffffffff81472684
>> #17 device_unregister at ffffffff814727e2
>> #18 xenbus_dev_changed at ffffffff813fa89f
>> #19 frontend_changed at ffffffff813fca19
>> #20 xenwatch_thread at ffffffff813f88f9
>> #21 kthread at ffffffff810a486b
>> #22 ret_from_fork at ffffffff816ed2a8
>>
>> Cc: [email protected]
>> Signed-off-by: Manjunath Patil <[email protected]>
> Commit f92898e7f32e3 already added that.
>
>
> Juergen