Re: [PATCH] sysfs: kill an extra put in sysfs_create_link() failure path

Satyam Sharma
2007-07-18T14:48:49Z

Hi Tejun,

Thanks for tracking this down and fixing it.

On 7/18/07, Tejun Heo <htejun@gmail.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.

The "symlink" is released? But the creation of the symlink is
precisely what failed here ... did it not?

> Fix it by making only the symlink node responsible for putting
> target_sd.

And again ... the changelog sounds confusing indeed, perhaps I'm
not familiar enough with sysfs symlink-related terminology/semantics.
Care to elaborate?

> 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 */

Wow. This looks like a very mysterious way to fix a mysterious bug :-)
BTW I just looked over at sysfs_create_link() and ... it looks quite ...
unnecessarily complicated/obfuscated ...

Thanks again,
Satyam