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authorTejun Heo <tj@kernel.org>2014-02-03 14:09:08 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-07 15:52:48 -0800
commit07c7530dd46728e25e938d0eb291f8085435c365 (patch)
treeaf31cc0ecb79794e1294b7781350afc45c1657d2
parentce8b04aa6c9bdf211b921fdd18c040ea29516b97 (diff)
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kernfs: invoke dir_ops while holding active ref of the target node
kernfs_dir_ops are currently being invoked without any active reference, which makes it tricky for the invoked operations to determine whether the objects associated those nodes are safe to access and will remain that way for the duration of such operations. kernfs already has active_ref mechanism to deal with this which makes the removal of a given node the synchronization point for gating the file operations. There's no reason for dir_ops to be any different. Update the dir_ops handling so that active_ref is held while the dir_ops are executing. This guarantees that while a dir_ops is executing the target nodes stay alive. As kernfs_dir_ops doesn't have any in-kernel user at this point, this doesn't affect anybody. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/kernfs/dir.c33
-rw-r--r--include/linux/kernfs.h3
2 files changed, 32 insertions, 4 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8c63ae1bccb6..bfbfb48f4ad8 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -654,22 +654,36 @@ static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
{
struct kernfs_node *parent = dir->i_private;
struct kernfs_dir_ops *kdops = kernfs_root(parent)->dir_ops;
+ int ret;
if (!kdops || !kdops->mkdir)
return -EPERM;
- return kdops->mkdir(parent, dentry->d_name.name, mode);
+ if (!kernfs_get_active(parent))
+ return -ENODEV;
+
+ ret = kdops->mkdir(parent, dentry->d_name.name, mode);
+
+ kernfs_put_active(parent);
+ return ret;
}
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ int ret;
if (!kdops || !kdops->rmdir)
return -EPERM;
- return kdops->rmdir(kn);
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ ret = kdops->rmdir(kn);
+
+ kernfs_put_active(kn);
+ return ret;
}
static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
@@ -678,11 +692,24 @@ static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
struct kernfs_node *kn = old_dentry->d_fsdata;
struct kernfs_node *new_parent = new_dir->i_private;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ int ret;
if (!kdops || !kdops->rename)
return -EPERM;
- return kdops->rename(kn, new_parent, new_dentry->d_name.name);
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ if (!kernfs_get_active(new_parent)) {
+ kernfs_put_active(kn);
+ return -ENODEV;
+ }
+
+ ret = kdops->rename(kn, new_parent, new_dentry->d_name.name);
+
+ kernfs_put_active(new_parent);
+ kernfs_put_active(kn);
+ return ret;
}
const struct inode_operations kernfs_dir_iops = {
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 02ac33435808..58a131ddc6a3 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -111,7 +111,8 @@ struct kernfs_node {
* kernfs_dir_ops may be specified on kernfs_create_root() to support
* directory manipulation syscalls. These optional callbacks are invoked
* on the matching syscalls and can perform any kernfs operations which
- * don't necessarily have to be the exact operation requested.
+ * don't necessarily have to be the exact operation requested. An active
+ * reference is held for each kernfs_node parameter.
*/
struct kernfs_dir_ops {
int (*mkdir)(struct kernfs_node *parent, const char *name,