linux-kernel - Re: [PATCH v2] xen-blkfront: fix kernel panic with negotiate

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Message-ID: <20181031082225.zp2cnrfuinpbilv5@mac.citrite.net>
Date:   Wed, 31 Oct 2018 09:22:25 +0100
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Manjunath Patil <manjunath.b.patil@...cle.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>, <stable@...r.kernel.org>
Subject: Re: [PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq
 error path

On Tue, Oct 30, 2018 at 09:49:21AM -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
> 
> Cc: stable@...r.kernel.org
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <manjunath.b.patil@...cle.com>

Acked-by: Roger Pau Monné <roger.pau@...rix.com>

Thanks, Roger.