linux-kernel - Re: [PATCH 2/3] scsi: megaraid_sas: check user-provided offsets

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Date:   Wed, 30 Dec 2020 16:15:53 -0800
From:   Phil Oester <kernel@...uxace.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kashyap Desai <kashyap.desai@...adcom.com>,
        Sumit Saxena <sumit.saxena@...adcom.com>,
        Shivasharan S <shivasharan.srikanteshwara@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        hch@...radead.org, Arnd Bergmann <arnd@...db.de>,
        stable@...r.kernel.org, Anand Lodnoor <anand.lodnoor@...adcom.com>,
        Chandrakanth Patil <chandrakanth.patil@...adcom.com>,
        Hannes Reinecke <hare@...e.de>, megaraidlinux.pdl@...adcom.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] scsi: megaraid_sas: check user-provided offsets

On Tue, Sep 08, 2020 at 11:36:22PM +0200, Arnd Bergmann wrote:
> It sounds unwise to let user space pass an unchecked 32-bit
> offset into a kernel structure in an ioctl. This is an unsigned
> variable, so checking the upper bound for the size of the structure
> it points into is sufficient to avoid data corruption, but as
> the pointer might also be unaligned, it has to be written carefully
> as well.
> 
> While I stumbled over this problem by reading the code, I did not
> continue checking the function for further problems like it.

Sorry for replying to an ancient thread, but this patch just recently
made it into 5.10.3 and has caused unintended consequences.  On Dell
servers with PERC RAID controllers, booting 5.10.3+ with this patch
causes a PCI parity error.  Specifically:

Event Message: A PCI parity error was detected on a component at bus 0 device 5 function 0.
Severity: Critical
Message ID: PCI1308

I reverted this single patch and the errors went away.

Thoughts?

Phil Oester