linux-kernel - Driver-Core: devtmpfs - reset inode permissions before unlinking

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Date:	Wed, 13 Jan 2010 14:16:36 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Greg KH <greg@...ah.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Driver-Core: devtmpfs - reset inode permissions before unlinking

From: Kay Sievers <kay.sievers@...y.org>
Subject: 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@...y.org>
---
 drivers/base/devtmpfs.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -301,6 +301,19 @@ int devtmpfs_delete_node(struct device *
 		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)


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