linux-kernel - Re: [Patch 7/9] fs/exec.c: fix wrong return value of prepare

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Date:	Mon, 12 May 2008 05:01:22 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	WANG Cong <xiyou.wangcong@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...l.org>,
	WANG Cong <wangcong@...ux.org>
Subject: Re: [Patch 7/9] fs/exec.c: fix wrong return value of
	prepare_binprm()

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...

>         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".
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