linux-kernel - Re: [scsi] 6aded12b10: kernel_BUG_at

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Date:   Wed, 23 Mar 2022 15:30:44 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@....de>,
        kernel test robot <oliver.sang@...el.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Bart Van Assche <bvanassche@....org>,
        John Garry <john.garry@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com, linux-mm@...ck.org, linux-hardening@...r.kernel.org
Subject: Re: [scsi]  6aded12b10: kernel_BUG_at_mm/usercopy.c

On Wed, Mar 23, 2022 at 03:42:34PM +0000, Matthew Wilcox wrote:
> On Wed, Mar 23, 2022 at 08:40:30AM -0700, Kees Cook wrote:
> > On Wed, Mar 23, 2022 at 08:14:10AM +0100, Christoph Hellwig wrote:
> > > The actual warning is;
> > > 
> > > [   34.496096][  T331] usercopy: Kernel memory overwrite attempt detected to spans multiple pages (off set 0, size 6)!
> > > 
> > > This is for the cmnd field in struct scsi_cmnd, which is allocated by
> > > the block layer as part of the request allocator.  So with a specific
> > > packing it can legitimately span pages.
> > > 
> > > Kees: how can we annotate that this is ok?
> > 
> > The main problem is that CONFIG_HARDENED_USERCOPY_PAGESPAN=y is broken
> > (and nothing should be setting it).
> > 
> > This series removes it:
> > https://lore.kernel.org/linux-hardening/20220110231530.665970-1-willy@infradead.org/
> > 
> > Matthew, what's the status of that series? Will it make the current
> > merge window?
> 
> I thought you were going to merge it!  I haven't put it in any of my
> public trees.

LOL. Okay, you'd mentioned another check, so I wasn't sure. I can go
ahead and snag it, but I'll likely wait until the next window and let it
live in -next for a while, unless you think it should get YOLOed in. :)

-Kees

-- 
Kees Cook