Driver-Core: devtmpfs - reset inode permissions before unlinking

Before unlinking the inode, reset the current permissions of possible
references like hardlinks, so granted permissions can not be retained
across the device lifetime by creating hardlinks, in the unusual case
that there is a user-writable directory on the same filesystem.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 42ae452b36b0c058376286882220ef25aff49c9e..dac478c6e46089c5bf8070dfa4127659b44fb6ec 100644 (file)
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -301,6 +301,19 @@ int devtmpfs_delete_node(struct device *dev)
                if (dentry->d_inode) {
                        err = vfs_getattr(nd.path.mnt, dentry, &stat);
                        if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
+                               struct iattr newattrs;
+                               /*
+                                * before unlinking this node, reset permissions
+                                * of possible references like hardlinks
+                                */
+                               newattrs.ia_uid = 0;
+                               newattrs.ia_gid = 0;
+                               newattrs.ia_mode = stat.mode & ~0777;
+                               newattrs.ia_valid =
+                                       ATTR_UID|ATTR_GID|ATTR_MODE;
+                               mutex_lock(&dentry->d_inode->i_mutex);
+                               notify_change(dentry, &newattrs);
+                               mutex_unlock(&dentry->d_inode->i_mutex);
                                err = vfs_unlink(nd.path.dentry->d_inode,
                                                 dentry);
                                if (!err || err == -ENOENT)