linux-kernel - Re: [Xen-devel] [PATCH] xen-blkfront: fix kernel panic with negotiate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Tue, 30 Oct 2018 09:29:02 -0700
From:   Manjunath Patil <manjunath.b.patil@...cle.com>
To:     Roger Pau Monné <roger.pau@...rix.com>
Cc:     boris.ostrovsky@...cle.com, jgross@...e.com,
        konrad.wilk@...cle.com, axboe@...nel.dk,
        xen-devel@...ts.xenproject.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen-blkfront: fix kernel panic with
 negotiate_mq error path

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@...cle.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