linux-kernel - Re: [PATCH] Off-by-one in /sys/module/*/refcnt

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Date:	Sun, 5 Aug 2007 16:00:08 +0200
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Alexey Dobriyan" <adobriyan@...il.com>,
	"Tejun Heo" <htejun@...il.com>
Cc:	akpm@...l.org, gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Off-by-one in /sys/module/*/refcnt

On 8/5/07, Alexey Dobriyan <adobriyan@...il.com> wrote:
> Hell knows when this changed, but sysfs is lying about modules refcounts now.
>
> $ cat /sys/module/it87/refcnt
> 4294967295
> $ lsmod | grep ^it87
> it87                   15756  0
>
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> ---
>
>  kernel/module.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -785,7 +785,7 @@ static ssize_t show_refcnt(struct module_attribute *mattr,
>                            struct module *mod, char *buffer)
>  {
>         /* sysfs holds a reference */
> -       return sprintf(buffer, "%u\n", module_refcount(mod)-1);
> +       return sprintf(buffer, "%u\n", module_refcount(mod));
>  }

It's likely caused by sysfs core changes, that opened attributes are
no longer coupled to the refcount of modules. They used to take a
reference.

The "holds a reference" comment should be removed along with your fix.
Adding Tejun, to confirm this.

Thanks,
Kay
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