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authorEric W. Biederman <ebiederm@xmission.com>2007-08-20 21:36:30 +0900
committerGreg Kroah-Hartman <gregkh@suse.de>2007-10-12 14:51:08 -0700
commit932ea2e374dd1ca26676297a5eccd1cdab86f7cd (patch)
tree83bba794de7f1f9f9290192f4f95a8ed9c91dfb6 /fs/sysfs/dir.c
parent89bec09705d2033b8b765f3c3ac5093f80bd5bc4 (diff)
downloadlinux-932ea2e374dd1ca26676297a5eccd1cdab86f7cd.tar.bz2
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>
Diffstat (limited to 'fs/sysfs/dir.c')
-rw-r--r--fs/sysfs/dir.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 1af963e66e3c..9fe83d23dc2c 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -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;
}