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Commit 932ea2e3 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Greg Kroah-Hartman
Browse files

sysfs: Introduce sysfs_rename_mutex 



Looking carefully at the rename code we have a subtle dependency
that the structure of sysfs not change while we are performing
a rename.  If the parent directory of the object we are renaming
changes while the rename is being performed nasty things could
happen when we go to release our locks.

So introduce a sysfs_rename_mutex to prevent this highly
unlikely theoretical issue.

In addition hold sysfs_rename_mutex over all calls to
sysfs_get_dentry. Allowing sysfs_get_dentry to be simplified
in the future.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 89bec097

fs/sysfs/dir.c

+7 −1
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include "sysfs.h"



DEFINE_MUTEX(sysfs_mutex);

DEFINE_MUTEX(sysfs_rename_mutex);

spinlock_t sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;



static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
@@ -82,7 +83,7 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd) 
 *	down from there looking up dentry for each step.

 *

 *	LOCKING:

 *	Kernel thread context (may sleep)

 *	mutex_lock(sysfs_rename_mutex)

 *

 *	RETURNS:

 *	Pointer to found dentry on success, ERR_PTR() value on error.
@@ -858,6 +859,8 @@ int sysfs_rename_dir(struct kobject * kobj, const char *new_name) 
	const char *dup_name = NULL;

	int error;



	mutex_lock(&sysfs_rename_mutex);



	/* get the original dentry */

	sd = kobj->sd;

	old_dentry = sysfs_get_dentry(sd);
@@ -915,6 +918,7 @@ int sysfs_rename_dir(struct kobject * kobj, const char *new_name) 
	kfree(dup_name);

	dput(old_dentry);

	dput(new_dentry);

	mutex_unlock(&sysfs_rename_mutex);

	return error;

}
@@ -926,6 +930,7 @@ int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj) 
	struct dentry *old_dentry = NULL, *new_dentry = NULL;

	int error;



	mutex_lock(&sysfs_rename_mutex);

	BUG_ON(!sd->s_parent);

	new_parent_sd = new_parent_kobj->sd ? new_parent_kobj->sd : &sysfs_root;
@@ -982,6 +987,7 @@ again: 
	dput(new_parent);

	dput(old_dentry);

	dput(new_dentry);

	mutex_unlock(&sysfs_rename_mutex);

	return error;

}

fs/sysfs/file.c

+4 −0
Original line number Diff line number Diff line
@@ -470,7 +470,9 @@ int sysfs_update_file(struct kobject * kobj, const struct attribute * attr) 
	if (!victim_sd)

		goto out;



	mutex_lock(&sysfs_rename_mutex);

	victim = sysfs_get_dentry(victim_sd);

	mutex_unlock(&sysfs_rename_mutex);

	if (IS_ERR(victim)) {

		rc = PTR_ERR(victim);

		victim = NULL;
@@ -509,7 +511,9 @@ int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode) 
	if (!victim_sd)

		goto out;



	mutex_lock(&sysfs_rename_mutex);

	victim = sysfs_get_dentry(victim_sd);

	mutex_unlock(&sysfs_rename_mutex);

	if (IS_ERR(victim)) {

		rc = PTR_ERR(victim);

		victim = NULL;

fs/sysfs/sysfs.h

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr); 


extern spinlock_t sysfs_assoc_lock;

extern struct mutex sysfs_mutex;

extern struct mutex sysfs_rename_mutex;

extern struct super_block * sysfs_sb;

extern const struct file_operations sysfs_dir_operations;

extern const struct file_operations sysfs_file_operations;