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Date: Mon, 12 May 2008 12:15:34 +0800
From: WANG Cong <xiyou.wangcong@gmail.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: WANG Cong <xiyou.wangcong@gmail.com>, LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, WANG Cong <wangcong@zeuux.org>
Subject: Re: [Patch 7/9] fs/exec.c: fix wrong return value of
	prepare_binprm()
Message-ID: <20080512041534.GG2572@hacking>
References: <1210254754206-git-send-email-xiyou.wangcong@gmail.com> <12102548553947-git-send-email-xiyou.wangcong@gmail.com> <20080510193105.GG13907@ZenIV.linux.org.uk> <20080512035643.GE2572@hacking> <20080512040122.GN13907@ZenIV.linux.org.uk>
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On Mon, May 12, 2008 at 05:01:22AM +0100, Al Viro wrote:
>On Mon, May 12, 2008 at 11:56:43AM +0800, WANG Cong wrote:
>> On Sat, May 10, 2008 at 08:31:05PM +0100, Al Viro wrote:
>> >On Thu, May 08, 2008 at 09:52:32PM +0800, WANG Cong wrote:
>> >> All prepare_binprm()'s callers assume that prepare_binprm() fails
>> >> when it returns negative. However, prepare_binprm() most probably returns
>> >> the return value of kernel_read(), which may return positive on failure!
>> >> 
>> >> Thus this should be fixed.
>> >
>> >Since when does read return positive on failure?
>> 
>> When an EIO occurs, I think. For example,
>
>No.  On EIO it returns -EIO, TYVM...
>

Hmm, it should. Thanks for your correction.


>>         retval = kernel_read(interpreter, interp_elf_ex->e_phoff,
>>                              (char *)elf_phdata,size);
>>         error = -EIO;
>>         if (retval != size) {
>>                 if (retval < 0)
>>                         error = retval;
>>                 goto out_close;
>>         }
>
>Which is what we do on short read here.  FWIW, -EINVAL might be saner
>choice - it's "binary is corrupted", not "read had failed".

IMO, -EIO is fine, because -EINVAL means "Invalid argument", but
there's nothing wrong with arguments here, just some bad things occurred
on reading the binary.

And even if it is really "binary is corrupted", then -ENOEXEC is
better than -EINVAL, isn't it?

Anyway, kernel_read() may return postive when not success.

Thanks.

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