Re: [Patch 7/9] fs/exec.c: fix wrong return value of prepare_binprm()

[Al Viro <viro@ZenIV.linux.org.uk>]

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".