linux-kernel - Re: [PATCH] sysfs: kill an extra put in sysfs_create

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Date:	Wed, 18 Jul 2007 07:29:17 -0700
From:	"Miles Lane" <miles.lane@...il.com>
To:	"Tejun Heo" <htejun@...il.com>
Cc:	"Gabriel C" <nix.or.die@...glemail.com>,
	"Satyam Sharma" <satyam.sharma@...il.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Christoph Lameter" <clameter@....com>, gregkh@...e.de
Subject: Re: [PATCH] sysfs: kill an extra put in sysfs_create_link() failure path

On 7/18/07, Tejun Heo <htejun@...il.com> wrote:
> There is a subtle bug in sysfs_create_link() failure path.  When
> symlink creation fails because there's already a node with the same
> name, the target sysfs_dirent is put twice - once by failure path of
> sysfs_create_link() and once more when the symlink is released.
>
> Fix it by making only the symlink node responsible for putting
> target_sd.
>
> Signed-off-by: Tejun Heo <htejun@...il.com>
> ---
> Gabriel, Miles, please verify this fixes your problem.  Thanks.
>
>  fs/sysfs/symlink.c |    2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
> index 2f86e04..d056e96 100644
> --- a/fs/sysfs/symlink.c
> +++ b/fs/sysfs/symlink.c
> @@ -86,7 +86,9 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
>         sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
>         if (!sd)
>                 goto out_put;
> +
>         sd->s_elem.symlink.target_sd = target_sd;
> +       target_sd = NULL;       /* reference is now owned by the symlink */
>
>         sysfs_addrm_start(&acxt, parent_sd);
>
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>

Great!  I tested with both patches applied to 2.6.22-rc6-mm1 and was
able to remove ipw2200 without triggering the BUG.

Thanks,
            Miles
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