netdev - Re: [PATCH net-next 1/2] bonding: add sysfs /slave dir for bond slave devices.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <B1B4CB0E-6A3C-4023-9911-D57B5F58D691@cumulusnetworks.com>
Date:	Thu, 16 Jan 2014 10:04:31 -0800
From:	Scott Feldman <sfeldma@...ulusnetworks.com>
To:	Veaceslav Falico <vfalico@...hat.com>
Cc:	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Netdev <netdev@...r.kernel.org>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	Shrijeet Mukherjee <shm@...ulusnetworks.com>
Subject: Re: [PATCH net-next 1/2] bonding: add sysfs /slave dir for bond slave devices.


On Jan 16, 2014, at 7:31 AM, Veaceslav Falico <vfalico@...hat.com> wrote:

> On Wed, Jan 15, 2014 at 09:54:34PM -0800, Scott Feldman wrote:
>> Add sub-directory under /sys/class/net/<interface>/slave with
>> read-only attributes for slave.  Directory only appears when
>> <interface> is a slave.

>> +static ssize_t state_show(struct slave *slave, char *buf)
>> +{
>> +	switch (bond_slave_state(slave)) {
>> +	case BOND_STATE_ACTIVE:
>> +		return sprintf(buf, "active\n");
>> +	case BOND_STATE_BACKUP:
>> +		return sprintf(buf, "backup\n");
>> +	default:
>> +		return sprintf(buf, "UNKONWN\n");
>> +	}
>> +}
>> +static SLAVE_ATTR_RO(state);
> 
> Am I missing something or does it really completely lacks any locking?
> 
> What prevents the slave to be freed in between?

Correct me if I’m wrong, but I think the equivalent question is: is there a race between sysfs_remove_file() and another CPU open on that file trying to read/write the file?  I believe the answer is no, but I’ll defer to the experts.

The file removal call path is:

	
	bond_release (ndo_del_slave)
		__bond_release_one
			bond_sysfs_slave_del
				sysfs_remove_file
			<...continue freeing slave...>

So slave is freed after sysfs_remove_file.  I would expect I/O on sysfs file to fail during sysfs_remove_file.

Does this sound OK?  Am I missing anything else?

-scott
		--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html