Re: [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

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