linux-kernel - Re: [PATCH v2] block: avoid false positive warnings on ioctl to partition

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Date:	Wed, 29 Feb 2012 09:13:08 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
	stable@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v2] block: avoid false positive warnings on ioctl to partition

Il 29/02/2012 01:14, Linus Torvalds ha scritto:
> So I'm still not convinced this is safe, and feel a bit worried about
> us possibly silently missing some things. That
> 
>    default:
>       return -ENOIOCTLCMD;
> 
> is what worries me.
> 
> Blocking the ones we *know* about and understand I'm perfectly fine
> with. And the SG_IO case looks fine. It's the possibly unknown users
> that still worry me.

I understand.

We do have a good grasp of what's happening.  We did get reports for
SG_IO, for false positives that would have returned -ENOTTY, and for
ioctls that need to be passed.  We couldn't expect anything better than
this, I think.

I checked in the source and all scsi_host-specific ioctls need
filtering.  Of course we might be missing something really obscure which
is rarely used in the wild.  But being 100% sure that nothing breaks is
impossible, unfortunately, so does it make sense to aim at 100%?  And it
should be extremely easy to bisect failures.  Even with all the
differences, it reminds me of the recent change to poll.

Paolo
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