linux-kernel - [085/145] Driver-Core: devtmpfs - reset inode permissions before unlinking

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Message-Id: <20100313002712.641656529@kvm.kroah.org>
Date:	Fri, 12 Mar 2010 16:26:58 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Kay Sievers <kay.sievers@...y.org>
Subject: [085/145] Driver-Core: devtmpfs - reset inode permissions before unlinking

2.6.32-stable review patch.  If anyone has any objections, please let me know.

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

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@...y.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/base/devtmpfs.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -295,6 +295,19 @@ 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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