linux-kernel - RE: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 Sep 2020 02:01:34 +0000
From:   "Zhao, Haifeng" <haifeng.zhao@...el.com>
To:     Sinan Kaya <okaya@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "oohall@...il.com" <oohall@...il.com>,
        "ruscur@...sell.cc" <ruscur@...sell.cc>,
        "lukas@...ner.de" <lukas@...ner.de>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "stuart.w.hayes@...il.com" <stuart.w.hayes@...il.com>,
        "mr.nuke.me@...il.com" <mr.nuke.me@...il.com>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        Keith Busch <keith.busch@...el.com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jia, Pei P" <pei.p.jia@...el.com>,
        "ashok.raj@...ux.intel.com" <ashok.raj@...ux.intel.com>,
        "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@...el.com>
Subject: RE: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC
 before handling DLLSC and PDC

Sinan,
   I explained the reason why locks don't protect this case in the patch description part. 
Write side and read side hold different semaphore and mutex.

Thanks,
Ethan

-----Original Message-----
From: Sinan Kaya <okaya@...nel.org> 
Sent: Sunday, September 27, 2020 11:28 PM
To: Zhao, Haifeng <haifeng.zhao@...el.com>; bhelgaas@...gle.com; oohall@...il.com; ruscur@...sell.cc; lukas@...ner.de; andriy.shevchenko@...ux.intel.com; stuart.w.hayes@...il.com; mr.nuke.me@...il.com; mika.westerberg@...ux.intel.com; Keith Busch <keith.busch@...el.com>
Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; Jia, Pei P <pei.p.jia@...el.com>; ashok.raj@...ux.intel.com; Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@...el.com>
Subject: Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC

On 9/26/2020 11:28 PM, Ethan Zhao wrote:
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 53433b37e181..6f271160f18d 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -710,8 +710,10 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
>  	down_read(&ctrl->reset_lock);
>  	if (events & DISABLE_SLOT)
>  		pciehp_handle_disable_request(ctrl);
> -	else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC))
> +	else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC)) {
> +		pci_wait_port_outdpc(pdev);
>  		pciehp_handle_presence_or_link_change(ctrl, events);
> +	}
>  	up_read(&ctrl->reset_lock);

This looks like a hack TBH.

Lukas, Keith;

What is your take on this?
Why is device lock not protecting this situation?

Is there a lock missing in hotplug driver?

Sinan