linux-kernel - Re: [PATCH 2/2] Perform check in iov_iter_fault_in_readable() by check_readable

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Message-ID: <20090515093838.GB16682@one.firstfloor.org>
Date:	Fri, 15 May 2009 11:38:38 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Vitaly Mayatskikh <v.mayatskih@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Josef Bacik <josef@...hat.com>,
	sandeen@...hat.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Perform check in iov_iter_fault_in_readable() by check_readable_bytes()

> ptr = mmap(0, page_size, ....);
> ...
> write(fd, ptr + page_size - 256, 512);
> 
> Write() will fail here, but it can write first 256 bytes. Previously,
> all 512 bytes were proceeded, but last 256 bytes were zeroed, and
> sys_write() returned 256. Not very nice too. 

Is that really something that users rely on? It looks like a seriously
broken user program. Which one is that? (just that I can avoid it :)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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