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Date: Fri, 13 Jan 2006 19:44:04 -0800
From: Greg KH <greg@kroah.com>
To: Chuck Ebbert <76306.1226@compuserve.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch] kobject: don't oops on null kobject.name
Message-ID: <20060114034404.GA23061@kroah.com>
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On Fri, Jan 13, 2006 at 10:07:33PM -0500, Chuck Ebbert wrote:
> In-Reply-To: <20060114000246.GA7549@kroah.com>
> 
> On Fri, 13 Jan 2006, Greg KH wrote:
> 
> > Hm, I looked at the only user of kobjects in the kernel that I know of
> > that doesn't use sysfs (the cdev code) and even it sets the kobject name
> > to something sane, so I think we should be safe with this.
> 
> Well, something is still wrong.
> 
> I applied your patch to prevent registration of objects with null names on
> top of my patch, then applied this to see if my test still triggered, and
> the message was printed:

What was the message?  What traceback?

So, I think the point is that it isn't a kobject_add() issue, right?


> 
> 
> --- 2.6.15a.orig/lib/kobject.c
> +++ 2.6.15a/lib/kobject.c
> @@ -72,8 +72,10 @@ static int get_kobj_path_length(struct k
>  	 * Add 1 to strlen for leading '/' of each level.
>  	 */
>  	do {
> -		if (kobject_name(parent) == NULL)
> +		if (kobject_name(parent) == NULL) {
> +			printk("get_kobj_path_length: encountered NULL name\n");
>  			return 0;
> +		}
>  		length += strlen(kobject_name(parent)) + 1;
>  		parent = parent->parent;
>  	} while (parent);
> 
> 
> To reproduce:
> 
> Start with vanilla 2.6.15 and apply the three patches, which I called:
> 
>         kobject_dont_register_null_name.patch  <- my original
>         kobject_handle_null_object_name.patch  <- Greg's
>         kobject_debug_null_path.patch          <- included above
> 
> On a machine with an ATAPI CD-ROM, boot with "hdx=ide-scsi" where
> hdx is the CD-ROM's drivename.  Then try to mount a CD:
> 
>         mount -t iso9660 /dev/hdx /mnt/cdrom
> 
> Note that hdx is being controlled by ide-scsi so this should fail.  You
> will see the message from my new patch print in the kernel log.
> 
> NOTE:  This won't happen on 2.6.15-current because
> fs/super.c::kill_block_super() no longer calls kobject_uevent().

So everything's fixed and we don't have to worry about it anymore :)

Seriously, I agree, we still need to fix it for -stable.

thanks,

greg k-h