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>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 42ae452b36b0..dac478c6e460 100644
--- 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)