From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kay Sievers <kay@vrfy.org>,
linux-next@vger.kernel.org
Subject: Re: [BUG -next] sysfs change breaks userspace
Date: Fri, 1 Nov 2013 15:13:48 +0100 [thread overview]
Message-ID: <20131101141348.GA5411@osiris> (raw)
In-Reply-To: <20131031172506.GE11698@mtj.dyndns.org>
On Thu, Oct 31, 2013 at 01:25:06PM -0400, Tejun Heo wrote:
> Hello, Heiko.
>
> On Thu, Oct 31, 2013 at 12:43:58PM +0100, Heiko Carstens wrote:
> > Hi Tejun,
> >
> > I just tried out linux-next and my network doesn't come up anymore.
> > Userspace fails like this:
> >
> > network[2211]: Bringing up interface eth0: sysfs read broadcast value: Invalid argument
> >
> > I bisected that down to:
> >
> > commit 13c589d5b0ac654d9da7e490a2dd548e6b86b4a5
> > Author: Tejun Heo <tj@kernel.org>
> > Date: Tue Oct 1 17:42:02 2013 -0400
> >
> > sysfs: use seq_file when reading regular files
>
> Heh, intereting. The content doesn't change over multiple show
> invocations, so the behavior shouldn't change at all for the attribute
> and seq_file handles seeking and partial reads correctly. No idea
> what could go wrong there. It probably was reading
> /sys/devices/BLAHBLAH/net/NETIF/broadcast file. Can you please locate
> the file and do "ls -l" and "cat" on it? If that looks normal, can
> you please strace the network interface config program / script /
> whatever? BTW, what are you running on the system?
Ok, here we go:
before your patch it was like this:
[pid 2888] open("/sys/class/net/eth0/broadcast", O_RDONLY) = 5
[pid 2888] lseek(5, 0, SEEK_END) = 4096
[pid 2888] lseek(5, 0, SEEK_SET) = 0
[pid 2888] read(5, "ff:ff:ff:ff:ff:ff\n", 4096) = 18
[pid 2888] close(5) = 0
With your patch applied I get this:
[pid 2450] open("/sys/class/net/eth0/broadcast", O_RDONLY) = 5
[pid 2450] lseek(5, 0, SEEK_END) = -1 EINVAL (Invalid argument)
[pid 2450] lseek(5, 0, SEEK_SET) = 0
[pid 2450] read(5, 0x557421e8, 4294967295) = -1 EINVAL (Invalid argument)
[pid 2450] close(5) = 0
So the problem is that lseek with SEEK_END doesn't work.
Afterwards the process tried to use the return value of lseek as number of
bytes to be read, which doesn't work ;)
This is a Fedora 17 like system on s390. It's a bit special since the kernel
is 64 bit and whole user space is 32 bit.
next prev parent reply other threads:[~2013-11-01 14:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-31 11:43 [BUG -next] sysfs change breaks userspace Heiko Carstens
2013-10-31 17:25 ` Tejun Heo
2013-11-01 14:13 ` Heiko Carstens [this message]
2013-11-01 14:35 ` Tejun Heo
2013-11-01 15:04 ` Greg Kroah-Hartman
2013-11-01 15:08 ` Tejun Heo
2013-11-01 16:14 ` Greg Kroah-Hartman
2013-11-01 17:16 ` [PATCH driver-core-next] sysfs: use generic_file_llseek() for sysfs_file_operations Tejun Heo
2013-11-01 17:19 ` Greg Kroah-Hartman
2013-11-01 18:40 ` Heiko Carstens
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