Subject: Re: Error returns not
	handled	correctly	by	sysfs.c:subsys_attr_store()
From: Andrew Patterson <andrew.patterson@hp.com>
To: Tejun Heo <teheo@suse.de>
Cc: Greg KH <greg@kroah.com>, Andrew Morton <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org, linux-hotplug@vger.kernel.org,
       bjorn.helgaas@hp.com
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Date: Thu, 03 Jan 2008 17:56:13 -0700
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On Thu, 2008-01-03 at 17:17 -0700, Andrew Patterson wrote:
> On Fri, 2008-01-04 at 09:07 +0900, Tejun Heo wrote:
> > Hello,
> > 
> > Andrew Patterson wrote:
> > > It looks like this is a shell issue.  After looking through the sysfs
> > > code, I realized that this problem seems to be driven from user-land.
> > > So I performed some experiments:
> > > 
> > >      1. Wrote a simple program that just used write(2) to write to the
> > >         sysfs entry. This works fine.
> > >      2. Used /bin/echo instead of the built-in echo command.  This too
> > >         works fine.
> > >      3. Tried several shells.  Zsh and Bash both fail.  Csh works fine.
> > > 
> > > I then ran strace on the following shell-script:
> > > 
> > > #!/bin/bash
> > > 
> > > echo x > allow_restart
> > > echo y > allow_restart
> > > echo z > allow_restart
> > > 
> > > and got:
> > > 
> > > # strace -e trace=write ~/tmp/tester.sh 
> > > write(1, "x\n", 2)                      = -1 EINVAL (Invalid argument)
> > > write(1, "x\n", 2)                      = -1 EINVAL (Invalid argument)
> > > write(2, "/home/andrew/tmp/tester.sh: line"..., 72/home/andrew/tmp/tester.sh: line 4: echo: write error: Invalid argument
> > > ) = 72
> > > write(1, "x\ny\n", 4)                   = -1 EINVAL (Invalid argument)
> > > write(1, "x\ny\n", 4)                   = -1 EINVAL (Invalid argument)
> > > write(2, "/home/andrew/tmp/tester.sh: line"..., 72/home/andrew/tmp/tester.sh: line 5: echo: write error: Invalid argument
> > > ) = 72
> > > write(1, "x\ny\nz\n", 6)                = -1 EINVAL (Invalid argument)
> > > write(1, "x\ny\nz\n", 6)                = -1 EINVAL (Invalid argument)
> > > write(2, "/home/andrew/tmp/tester.sh: line"..., 72/home/andrew/tmp/tester.sh: line 6: echo: write error: Invalid argument
> > > ) = 72
> > > write(1, "x\ny\nz\n", 6x
> > > y
> > > z
> > > )                = 6
> > > Process 3800 detached
> > 
> > Eeeeeeeekkkk.... That's scary.  Which distro are you using and what does
> > 'bash --version' say?
> 
> IA64 Debian lenny.  
> 
> # bash --version
> GNU bash, version 3.1.17(1)-release (ia64-unknown-linux-gnu)
> 
> # zsh --version 
> zsh 4.3.4 (ia64-unknown-linux-gnu)
> 
> # csh --version
> tcsh 6.14.00 (Astron) 2005-03-25 (ia64-unknown-linux) options
> wide,nls,dl,al,kan,rh,nd,color,filec
> 
> I suppose I should try this an ia32 box again, and perhaps with some
> other distros.  I am not sure what the kernel can do about this, but it
> might be nice to report it to the shell maintainers.

Some further tests:

AMD running Debian lenny with i686 kernel -- fails.  
Bash version = 3.1.17(1)

Intel running Ubuntu/gutsy with i686 kernel -- fails.
Bash version = 3.2.25(1)

Itanium running SLES10 with ia64 kernel -- succeeds.
Bash version = 3.1.17(1)

BTW, I found a way to reproduce this without modifying the kernel.
The /sys/class/scsi_host/*/state sysfs store routine returns EINVAL if
an invalid state is written. So just echo 2 bad values to the the state
sysfs entry while running strace.

Andrew

-- 
Andrew Patterson
Hewlett-Packard Company

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