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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: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Eric W. Biederman 2007-08-20 21:36:30 +09:00 committed by Greg Kroah-Hartman
parent 89bec09705
commit 932ea2e374
3 changed files with 12 additions and 1 deletions
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8
fs/sysfs/dir.c
View File

@ -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;
}

4
fs/sysfs/file.c
View File

@ -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;

1
fs/sysfs/sysfs.h
View File

@ -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;