Re: Error returns not handled correctlyby sysfs.c:subsys_attr_store()

From: Andrew Patterson
Date: Wed Nov 28 2007 - 14:31:25 EST


On Wed, 2007-11-28 at 16:42 +0900, Tejun Heo wrote:
> Greg KH wrote:
> > On Mon, Nov 26, 2007 at 08:31:16PM -0800, Andrew Morton wrote:
> >> On Wed, 21 Nov 2007 15:16:59 -0700 Andrew Patterson <andrew.patterson@xxxxxx> wrote:
> >>
> >>> The buf in fs/sysfs.c:subsys_attr_store() does not seem to be updated
> >>> correctly when returning a negative value (indicating that an error
> >>> condition has occurred) is returned. If a negative value is returned,
> >>> the next subsequent call to subsys_attr_store will have the contents of
> >>> buf appended to the previous call.
> >> subsys_attr_store() gets deleted by
> >> http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/gregkh-01-driver/kset-kill-subsys-attr.patch
> >>
> >> So maybe we will soon accidentally fix whatever-this-is? Or maybe we will
> >> faithfully maintain it.
> >
> > Yes, subsys attributes go away, but this is showing a bug in the sysfs
> > core with attributes, not in the "middle" layers of attributes.
> >
> > I bounced the original bug report to Tejun, who has been changing the
> > logic around this area to see if he sees anything that might be
> > different now.
> >
> > Tejun?
>
> Weird, the problem is not reproducible here.
>
> # echo a > allow_restart
> -bash: echo: write error: Invalid argument
> [ 437.518024] buf_ptr = 0xffff810005e20000, buf = x
> [ 437.518027] , count = 2
> # echo b > allow_restart
> -bash: echo: write error: Invalid argument
> [ 438.972973] buf_ptr = 0xffff81001be6f000, buf = y
> [ 438.972976] , count = 2
> # echo c > allow_restart
> -bash: echo: write error: Invalid argument
> [ 440.539747] buf_ptr = 0xffff81001d4ba000, buf = z
> [ 440.539750] , count = 2
>
> Which is expected. On each open, sysfs_buffer is allocated with kzalloc
> and the buffer is freed on close, so I don't see how it can happen.
> Behavior for multiple write can be considered peculiar in that ppos is
> essentially ignored and each write is passed just like brand new write
> to ->store method but this too is the expected behavior.
>
> # (echo a; echo b; echo c) > allow_restart
> [ 765.257132] buf_ptr = 0xffff81001be4f000, buf = a
> [ 765.257135] , count = 2
> [ 765.285474] buf_ptr = 0xffff81001be4f000, buf = b
> [ 765.285484] , count = 2
> [ 765.314002] buf_ptr = 0xffff81001be4f000, buf = c
> [ 765.314004] , count = 2
> -bash: echo: write error: Invalid argument
> -bash: echo: write error: Invalid argument
> -bash: echo: write error: Invalid argument
>
> Andrew Petterson, can you please build 2.6.24-rc3 from clean source tree
> and retry?
>

I tried with clean 2.6.24-rc3 and get the same bad behavior. This is on
an ia64 box, so maybe that is an issue. I can try on an x86 box as well.
Oh, one other thing. I tried a "uname -r" to make sure I had the
correct kernel booted and got:

# uname -r
2.6.24-rc3
x
y
z
#

Andrew
--
Andrew Patterson
Hewlett-Packard

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