linux-kernel - Re: [PATCH] aio: Fix type of iterator variable in do_io

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Message-ID: <20140423144237.GY22552@kvack.org>
Date:	Wed, 23 Apr 2014 10:42:37 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Matthew Wilcox <willy@...ux.intel.com>
Cc:	Eric Biggers <ebiggers3@...il.com>, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] aio: Fix type of iterator variable in do_io_submit()

On Wed, Apr 23, 2014 at 10:16:17AM -0400, Matthew Wilcox wrote:
> On Tue, Apr 22, 2014 at 05:57:03PM -0500, Eric Biggers wrote:
> > do_io_submit() iterated over the userspace iocb structure pointers using
> > a variable i of type 'int'.  This was wrong since 'nr', the number of
> > iocb structure pointers, could potentially be up to LONG_MAX /
> > sizeof(struct iocb *).  Fix it (and also remove the unnecessary
> > initialization to 0).
> 
> You're not wrong, but do we *really* want users to be able to submit
> 144115188075855872 I/Os with a single system call?  How about limiting
> them to a single billion?  Given that they have to allocate 64GB of
> *control* data structures to submit this many I/Os, I think this will
> be sufficient for many years to come.

Practically speaking, this change has no effect.  The io_submit() syscall 
will exit far before we even hit INT_MAX because of the limits on the 
number of iocbs.

		-ben
-- 
"Thought is the essence of where you are now."
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