Driver-Core: devtmpfs - reset inode permissions before unlinking

commit 5e31d76f2817bd50258a092a7c5b15b3006fd61c upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 33faaa22a19dae234e7bfe97b5d25f1eabb8e645..4d809667815e5d64ba72ef6b57146c8174d87170 100644 (file)
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -295,6 +295,19 @@ 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)