linux-kernel - [PATCH 11/11] evm: Don't update hmacs in user ns mounts

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Message-Id: <1f2233a1a028f1eb1e9bea7d06efa6d34e69e752.1512041070.git.dongsu@kinvolk.io>
Date:   Fri, 22 Dec 2017 15:32:35 +0100
From:   Dongsu Park <dongsu@...volk.io>
To:     linux-kernel@...r.kernel.org
Cc:     containers@...ts.linux-foundation.org,
        Alban Crequy <alban@...volk.io>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        Sargun Dhillon <sargun@...gun.me>,
        Dongsu Park <dongsu@...volk.io>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James Morris <james.l.morris@...cle.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>
Subject: [PATCH 11/11] evm: Don't update hmacs in user ns mounts

From: Seth Forshee <seth.forshee@...onical.com>

The kernel should not calculate new hmacs for mounts done by
non-root users. Update evm_calc_hmac_or_hash() to refuse to
calculate new hmacs for mounts for non-init user namespaces.

Cc: linux-integrity@...r.kernel.org
Cc: linux-security-module@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: James Morris <james.l.morris@...cle.com>
Cc: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
Signed-off-by: Dongsu Park <dongsu@...volk.io>
---
 security/integrity/evm/evm_crypto.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index bcd64baf..729f4545 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -190,7 +190,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 	int error;
 	int size;
 
-	if (!(inode->i_opflags & IOP_XATTR))
+	if (!(inode->i_opflags & IOP_XATTR) ||
+	    inode->i_sb->s_user_ns != &init_user_ns)
 		return -EOPNOTSUPP;
 
 	desc = init_desc(type);
-- 
2.13.6