linux-kernel - [PATCH 12/13] ovl-switch-to-inode

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Date:	Tue, 12 Mar 2013 16:41:47 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	viro@...IV.linux.org.uk, torvalds@...ux-foundation.org
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, akpm@...ux-foundation.org, apw@...onical.com,
	nbd@...nwrt.org, neilb@...e.de, jordipujolp@...il.com,
	ezk@....cs.sunysb.edu, dhowells@...hat.com,
	sedat.dilek@...glemail.com, hooanon05@...oo.co.jp, mszeredi@...e.cz
Subject: [PATCH 12/13] ovl-switch-to-inode_permission

From: Andy Whitcroft <apw@...onical.com>

When checking permissions on an overlayfs inode we do not take into
account either device cgroup restrictions nor security permissions.
This allows a user to mount an overlayfs layer over a restricted device
directory and by pass those permissions to open otherwise restricted
files.

Switch over to __inode_permissions.

Signed-off-by: Andy Whitcroft <apw@...onical.com>
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
 fs/overlayfs/inode.c |   12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 033de6f..3218a38 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -100,19 +100,9 @@ int ovl_permission(struct inode *inode, int mask)
 		if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
 			goto out_dput;
-
-		/*
-		 * Nobody gets write access to an immutable file.
-		 */
-		err = -EACCES;
-		if (IS_IMMUTABLE(realinode))
-			goto out_dput;
 	}
 
-	if (realinode->i_op->permission)
-		err = realinode->i_op->permission(realinode, mask);
-	else
-		err = generic_permission(realinode, mask);
+	err = __inode_permission(realinode, mask);
 out_dput:
 	dput(alias);
 	return err;
-- 
1.7.10.4

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