linux-kernel - [PATCH 18/62] Driver-Core: devtmpfs - reset inode permissions before unlinking

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Date:	Tue,  2 Mar 2010 15:28:17 -0800
From:	Greg Kroah-Hartman <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org
Cc:	Kay Sievers <kay.sievers@...y.org>, stable <stable@...nel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH 18/62] Driver-Core: devtmpfs - reset inode permissions before unlinking

From: Kay Sievers <kay.sievers@...y.org>

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>
Cc: stable <stable@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/base/devtmpfs.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 42ae452..dac478c 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)
-- 
1.7.0.1

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