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Subject: Re: [PATCH] mtd: maps: pcmciamtd: fix possible
 sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
To:     Dominik Brodowski <linux@dominikbrodowski.net>
Cc:     miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20191218140552.12249-1-baijiaju1990@gmail.com>
 <20191218172813.GA338501@light.dominikbrodowski.net>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <42939a91-baab-54ad-bb4c-8a77e4418f2f@gmail.com>
Date:   Thu, 19 Dec 2019 10:32:24 +0800
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On 2019/12/19 1:28, Dominik Brodowski wrote:
> On Wed, Dec 18, 2019 at 10:05:52PM +0800, Jia-Ju Bai wrote:
>> The driver may sleep while holding a spinlock.
>> The function call path (from bottom to top) in Linux 4.19 is:
>>
>> drivers/pcmcia/pcmcia_resource.c, 312:
>> 	mutex_lock in pcmcia_fixup_vpp
>> drivers/mtd/maps/pcmciamtd.c, 309:
>> 	pcmcia_fixup_vpp in pcmciamtd_set_vpp
>> drivers/mtd/maps/pcmciamtd.c, 306:
>> 	_raw_spin_lock_irqsave in pcmciamtd_set_vpp
>>
>> drivers/pcmcia/pcmcia_resource.c, 312:
>> 	mutex_lock in pcmcia_fixup_vpp
>> drivers/mtd/maps/pcmciamtd.c, 312:
>> 	pcmcia_fixup_vpp in pcmciamtd_set_vpp
>> drivers/mtd/maps/pcmciamtd.c, 306:
>> 	_raw_spin_lock_irqsave in pcmciamtd_set_vp
>>
>> mutex_lock() may sleep at runtime.
> Thanks for noticing this issue.
>
>> To fix these bugs, pcmcia_fixup_vpp() is called without holding the
>> spinlock.
> I don't think that this is the right approach here -- we lose the protection
> against races in calls to pcmcia_fixup_vpp(). Instead, we should change the
> spinlock to a mutex, which seems to be sufficient here. Could you prepare
> such a patch, please?

Okay, thanks for the advice :)
I will send a new patch.


Best wishes,
Jia-Ju Bai