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From: Manjunath Patil <manjunath.b.patil@oracle.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: boris.ostrovsky@oracle.com, jgross@suse.com,
	konrad.wilk@oracle.com, axboe@kernel.dk,
	xen-devel@lists.xenproject.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen-blkfront: fix kernel panic with negotiate_mq error path
Date: Tue, 30 Oct 2018 09:29:02 -0700	[thread overview]
Message-ID: <f8b9a166-e844-018d-2186-b49f54fc6fbb@oracle.com> (raw)
In-Reply-To: <20181030103956.hew7gifjvpjviw7u@mac.citrite.net>

On 10/30/2018 3:39 AM, Roger Pau Monné wrote:

> On Mon, Oct 29, 2018 at 11:31:56AM -0700, Manjunath Patil wrote:
>> info->nr_rings isn't adjusted in case of ENOMEM error from
>> negotiate_mq(). This leads to kernel panic in error path.
>>
>> Typical call stack involving panic -
>>   #8 page_fault at ffffffff8175936f
>>      [exception RIP: blkif_free_ring+33]
>>      RIP: ffffffffa0149491  RSP: ffff8804f7673c08  RFLAGS: 00010292
>>   ...
>>   #9 blkif_free at ffffffffa0149aaa [xen_blkfront]
>>   #10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront]
>>   #11 blkback_changed at ffffffffa014ea8b [xen_blkfront]
>>   #12 xenbus_otherend_changed at ffffffff81424670
>>   #13 backend_changed at ffffffff81426dc3
>>   #14 xenwatch_thread at ffffffff81422f29
>>   #15 kthread at ffffffff810abe6a
>>   #16 ret_from_fork at ffffffff81754078
>>
>> Though either of my changes avoid the panic, I included both the
>> changes. This issue got introduced with "7ed8ce1 xen-blkfront: move
>> negotiate_mq to cover all cases of new VBDs"
>>
>> Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>
>> ---
>>   drivers/block/xen-blkfront.c |    7 +++++--
>>   1 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
>> index 429d201..dc8fe25 100644
>> --- a/drivers/block/xen-blkfront.c
>> +++ b/drivers/block/xen-blkfront.c
>> @@ -1350,8 +1350,10 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>>   	if (info->rq)
>>   		blk_mq_stop_hw_queues(info->rq);
>>   
>> -	for (i = 0; i < info->nr_rings; i++)
>> -		blkif_free_ring(&info->rinfo[i]);
>> +	if (info->rinfo) {
>> +		for (i = 0; i < info->nr_rings; i++)
>> +			blkif_free_ring(&info->rinfo[i]);
>> +	}
> I don't see the point in the if case here, you already fixed it by
> setting the nr_rings value which I think it's the correct way of
> fixing it.
>
> Thanks, Roger.
Thank you Roger for your comments.
I will exclude this change and send for review again.

-Thanks,
Manjunath

      reply	other threads:[~2018-10-30 16:29 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-29 18:31 Manjunath Patil
2018-10-30  7:04 ` Juergen Gross
2018-10-30 16:27   ` [Xen-devel] " Manjunath Patil
2018-10-30 10:39 ` Roger Pau Monné
2018-10-30 16:29   ` Manjunath Patil [this message]

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