netdev - Re: [PATCH] Fix Kernel Panic in bonding driver debugfs file: rlb_hash

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Message-ID: <554134D1.7070509@blackwall.org>
Date:	Wed, 29 Apr 2015 21:45:21 +0200
From:	Nikolay Aleksandrov <razor@...ckwall.org>
To:	Pai <vpai@...mai.com>, Jay Vosburgh <j.vosburgh@...il.com>,
	Veaceslav Falico <vfalico@...il.com>,
	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix Kernel Panic in bonding driver debugfs file: rlb_hash_table

On 04/29/2015 08:24 PM, Pai wrote:
> This patch fixes a Kernel Panic in bonding driver debugfs file: rlb_hash_table.
> 
> $> modprobe bonding mode=6
> $> cat /sys/kernel/debug/bonding/bond0/rlb_hash_table
> 
> This will crash the kernel. The struct alb_bond_info is initialized only when
> the bonding interface is initialized (ip link set bond0 up) and not at the time
> it is allocated. If we try to read the table before that, it'll result in a 
> kernel panic.
> 
> The patch applies against both net and net-next
> 
> Signed-off-by: Vishwanath Pai <vpai@...mai.com>
>  
Good catch, a few cosmetic nits below.

> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 089a402..806892a 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4510,6 +4510,8 @@ unsigned int bond_get_num_tx_queues(void)
>  int bond_create(struct net *net, const char *name)
>  {
>  	struct net_device *bond_dev;
> +	struct bonding *bond;
> +	struct alb_bond_info *bond_info;
Please arrange these longest to shortest line, it's easier to read.

>  	int res;
>  
>  	rtnl_lock();
> @@ -4523,6 +4525,14 @@ int bond_create(struct net *net, const char *name)
>  		return -ENOMEM;
>  	}
>  
> +	/*
> +	 * Initialize rx_hashtbl_used_head to RLB_NULL_INDEX.
> +	 * It is set to 0 by default which is wrong.
> +	 */
Multiline comment style of networking content is:
	/* text
	 * text
	 */

See: Documentation/networking/netdev-FAQ.txt

Alternatively you can create an inline with descriptive name that does the
initialization and wouldn't need the comment. Either way's fine by me.

Cheers,
 Nik

> +	bond = netdev_priv(bond_dev);
> +	bond_info = &(BOND_ALB_INFO(bond));
> +	bond_info->rx_hashtbl_used_head = RLB_NULL_INDEX;
> +
>  	dev_net_set(bond_dev, net);
>  	bond_dev->rtnl_link_ops = &bond_link_ops;
>  
> --
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