Date: Fri, 2 Jul 2004 16:08:35 -0700
From: Chris Wright <chrisw@osdl.org>
Subject: [PATCH] check attr updates in /proc

Any proc entry with default proc_file_inode_operations allow unauthorized
attribute updates.  This is very dangerous for proc entries that rely
solely on file permissions for open/read/write.

Signed-off-by: Chris Wright <chrisw@osdl.org>

===== fs/proc/generic.c 1.30 vs edited =====
Index: linux-2.6.7-ck/fs/proc/generic.c
===================================================================
--- linux-2.6.7-ck.orig/fs/proc/generic.c	2004-05-23 12:54:55.000000000 +1000
+++ linux-2.6.7-ck/fs/proc/generic.c	2004-07-08 00:58:43.076709752 +1000
@@ -230,14 +230,21 @@
 static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
 {
 	struct inode *inode = dentry->d_inode;
-	int error = inode_setattr(inode, iattr);
-	if (!error) {
-		struct proc_dir_entry *de = PDE(inode);
-		de->uid = inode->i_uid;
-		de->gid = inode->i_gid;
-		de->mode = inode->i_mode;
-	}
+	struct proc_dir_entry *de = PDE(inode);
+	int error;
+
+	error = inode_change_ok(inode, iattr);
+	if (error)
+		goto out;
 
+	error = inode_setattr(inode, iattr);
+	if (error)
+		goto out;
+	
+	de->uid = inode->i_uid;
+	de->gid = inode->i_gid;
+	de->mode = inode->i_mode;
+out:
 	return error;
 }