linux-kernel - Re: [PATCH] xen-blkfront: use a right index when checking requests

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Date:   Thu, 10 Aug 2017 10:43:45 +0100
From:   Roger Pau Monne <roger.pau@...rix.com>
To:     Munehisa Kamata <kamatam@...zon.com>
CC:     <linux-kernel@...r.kernel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        <xen-devel@...ts.xenproject.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH] xen-blkfront: use a right index when checking requests

On Wed, Aug 09, 2017 at 03:31:40PM -0700, Munehisa Kamata wrote:
> Since commit d05d7f40791c ("Merge branch 'for-4.8/core' of
> git://git.kernel.dk/linux-block") and 3fc9d690936f ("Merge branch
> 'for-4.8/drivers' of git://git.kernel.dk/linux-block"), blkfront_resume()
> has been using an index for iterating ring_info to check request when
> iterating blk_shadow in an inner loop. This seems to have been
> accidentally introduced during the massive rewrite of the block layer
> macros in the commits.
> 
> This may cause crash like this:
> 
> [11798.057074] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
> [11798.058832] IP: [<ffffffff814411fa>] blkfront_resume+0x10a/0x610
> ....
> [11798.061063] Call Trace:
> [11798.061063]  [<ffffffff8139ce93>] xenbus_dev_resume+0x53/0x140
> [11798.061063]  [<ffffffff8139ce40>] ? xenbus_dev_probe+0x150/0x150
> [11798.061063]  [<ffffffff813f359e>] dpm_run_callback+0x3e/0x110
> [11798.061063]  [<ffffffff813f3a08>] device_resume+0x88/0x190
> [11798.061063]  [<ffffffff813f4cc0>] dpm_resume+0x100/0x2d0
> [11798.061063]  [<ffffffff813f5221>] dpm_resume_end+0x11/0x20
> [11798.061063]  [<ffffffff813950a8>] do_suspend+0xe8/0x1a0
> [11798.061063]  [<ffffffff813954bd>] shutdown_handler+0xfd/0x130
> [11798.061063]  [<ffffffff8139aba0>] ? split+0x110/0x110
> [11798.061063]  [<ffffffff8139ac26>] xenwatch_thread+0x86/0x120
> [11798.061063]  [<ffffffff810b4570>] ? prepare_to_wait_event+0x110/0x110
> [11798.061063]  [<ffffffff8108fe57>] kthread+0xd7/0xf0
> [11798.061063]  [<ffffffff811da811>] ? kfree+0x121/0x170
> [11798.061063]  [<ffffffff8108fd80>] ? kthread_park+0x60/0x60
> [11798.061063]  [<ffffffff810863b0>] ?  call_usermodehelper_exec_work+0xb0/0xb0
> [11798.061063]  [<ffffffff810864ea>] ?  call_usermodehelper_exec_async+0x13a/0x140
> [11798.061063]  [<ffffffff81534a45>] ret_from_fork+0x25/0x30
> 
> Use the right index in the inner loop.
> 
> Fixes: d05d7f40791c ("Merge branch 'for-4.8/core' of git://git.kernel.dk/linux-block")
> Fixes: 3fc9d690936f ("Merge branch 'for-4.8/drivers' of git://git.kernel.dk/linux-block")
> Signed-off-by: Munehisa Kamata <kamatam@...zon.com>
> Reviewed-by: Thomas Friebel <friebelt@...zon.de>
> Reviewed-by: Eduardo Valentin <eduval@...zon.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Roger Pau Monne <roger.pau@...rix.com>
> Cc: xen-devel@...ts.xenproject.org
> Cc: stable@...r.kernel.org

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

Thanks, Roger.