From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH] Fix kobject_rename and !CONFIG_SYSFS v4 Date: Tue, 13 May 2008 22:03:04 -0700 Message-ID: <20080513220304.b2f5a588.akpm@linux-foundation.org> References: <20080512220232.GA16914@kroah.com> <4829A4BD.3020007@bull.net> <20080513164438.GA31563@kroah.com> <20080513201602.GA31578@kroah.com> <24291087.1210713535895.JavaMail.oracle@acsmt301.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Randy Dunlap , Greg KH , Al Viro , Benjamin Thery , Greg KH , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Daniel Lezcano , Pavel Emelyanov , "Serge E. Hallyn" , Tejun Heo To: ebiederm@xmission.com (Eric W. Biederman) Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 13 May 2008 21:39:45 -0700 ebiederm@xmission.com (Eric W. Biederman) wrote: > > When looking at kobject_rename I found two bugs with > that exist when sysfs support is disabled in the kernel. > > kobject_rename does not change the name on the kobject when > sysfs support is not compiled in. > > kobject_rename without locking attempts to check the > validity of a rename operation, which the kobject layer > simply does not have the infrastructure to do. > > This patch documents the previously unstated requirement of > kobject_rename that is the responsibility of the caller to > provide mutual exclusion and to be certain that the new_name > for the kobject is valid. > > This patch modifies sysfs_rename_dir in !CONFIG_SYSFS case > to call kobject_set_name to actually change the kobject_name. > > This patch removes the bogus and misleading check in kobject_rename > that attempts to see if a rename is valid. The check is bogus > because we do not have the proper locking. The check is misleading > because it looks like we can and do perform checking at the kobject > level that we don't. > > Changelog: > v4: Documentation typo fixes > > v2: Added a declaration of kboject_set_name to sysfs.h > so the code actually compiles with !CONFIG_SYSFS. > > Unscrambling the header dependencies so everything looks > beautiful is a project for another day. > > Signed-off-by: Eric W. Biederman > --- > Documentation/kobject.txt | 4 ++++ > drivers/base/core.c | 5 +++++ > include/linux/sysfs.h | 4 +++- > lib/kobject.c | 18 +++++------------- > 4 files changed, 17 insertions(+), 14 deletions(-) > > diff --git a/Documentation/kobject.txt b/Documentation/kobject.txt > index bf3256e..ac80d82 100644 > --- a/Documentation/kobject.txt > +++ b/Documentation/kobject.txt > @@ -118,6 +118,10 @@ the name of the kobject, call kobject_rename(): > > int kobject_rename(struct kobject *kobj, const char *new_name); > > +Note kobject_rename does not perform any locking or have a solid notion of > +what names are valid so the caller must provide their own sanity checking > +and serialization. > + > There is a function called kobject_set_name() but that is legacy cruft and > is being removed. If your code needs to call this function, it is > incorrect and needs to be fixed. > diff --git a/drivers/base/core.c b/drivers/base/core.c > index be288b5..ad68f4c 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -1171,6 +1171,11 @@ EXPORT_SYMBOL_GPL(device_destroy); > * device_rename - renames a device > * @dev: the pointer to the struct device to be renamed > * @new_name: the new name of the device > + * > + * It is the responsibility of the caller to provide mutual > + * exclusion between two different calls of device_rename > + * on the same device to ensure that new_name is valid and > + * won't conflict with other devices. > */ > int device_rename(struct device *dev, char *new_name) > { > diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h > index 7858eac..6e61033 100644 > --- a/include/linux/sysfs.h > +++ b/include/linux/sysfs.h > @@ -20,6 +20,8 @@ > struct kobject; > struct module; > > +extern int kobject_set_name(struct kobject *kobj, const char *name, ...) > + __attribute__((format(printf, 2, 3))); Duplicating the kobject_set_name() declaration in sysfs.h is rather a hack. It'd be better to move it into a new header file, included by both sysfs.h and kobject.h. Perhaps there are other declarations which can be moved with it.