linux-kernel - Re: [PATCH] pci: Fix a possible sleep-in-atomic bug in pci_set_power

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Message-ID: <511f30f4-1b9e-1b1a-aad8-6c0505b40e4e@163.com>
Date:   Mon, 9 Oct 2017 16:32:33 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     patrik.r.jakobsson@...il.com, airlied@...ux.ie,
        bhelgaas@...gle.com, forest@...ttletooquiet.net, simon@...anor.nu,
        scott@...heina.com, tvboxspy@...il.com, dan.a.cashman@...il.com,
        golubev.mikhail@...il.com, devel@...verdev.osuosl.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] pci: Fix a possible sleep-in-atomic bug in
 pci_set_power_state

Oh, sorry, I will send the patches for each driver.


Thanks,
Jia-Ju Bai

On 2017/10/9 16:17, Greg KH wrote:
> On Mon, Oct 09, 2017 at 04:16:20PM +0800, Jia-Ju Bai wrote:
>> The drivers vt6655 and gma500 call pci_set_power_state under a spinlock, which may sleep.
>> The function call paths are:
>> gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
>>    gma_resume_pci
>>      pci_set_power_state
>>        __pci_start_power_transition (drivers/pci/pci.c)
>>          msleep --> may sleep
>>
>> gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
>>    gma_resume_pci
>>      pci_enable_device
>>        pci_enable_device_flags (drivers/pci/pci.c)
>>          do_pci_enable_device
>>            pci_set_power_state
>>              __pci_start_power_transition
>>                msleep --> may sleep
>>
>> vt6655_suspend (acquire the spinlock) (drivers/staging/vt6655/device_main.c)
>>    pci_set_power_state
>>      __pci_start_power_transition (drivers/pci/pci.c)
>>        msleep --> may sleep
>>
>> To fix these bugs, msleep is replaced with mdelay in __pci_start_power_transition
>>
>> These bugs are found by my static analysis tool and my code review.
> Wait, no, why not fix the callers to not have a spinlock.  Those are the
> only users of these calls that are doing so incorrectly, don't change
> the PCI core for the fault of 2 broken drivers.
>
> thanks,
>
> greg k-h