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From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
Date: Wed, 18 Dec 2019 18:28:13 +0100	[thread overview]
Message-ID: <20191218172813.GA338501@light.dominikbrodowski.net> (raw)
In-Reply-To: <20191218140552.12249-1-baijiaju1990@gmail.com>

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?

Thanks,
	Dominik

  reply	other threads:[~2019-12-18 17:28 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 14:05 [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp() Jia-Ju Bai
2019-12-18 17:28 ` Dominik Brodowski [this message]
2019-12-19  2:32   ` Jia-Ju Bai
  -- strict thread matches above, loose matches on Subject: below --
2019-12-18 13:41 Jia-Ju Bai

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