diff mbox

evm: Don't update hmacs in user ns mounts

Message ID 87r2mtybhf.fsf@xmission.com (mailing list archive)
State New, archived
Headers show

Commit Message

Eric W. Biederman May 2, 2018, 9:49 p.m. UTC
From: Seth Forshee <seth.forshee@canonical.com>
Date: Fri, 22 Dec 2017 15:32:35 +0100

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@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: James Morris <james.l.morris@oracle.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---

Mimi this patch has been floating around for a while and it appears to
be the only piece missing from the vfs to make unprivileged mounts safe
(at least semantically).  Do you want to merge this through your integrity
tree or should merge this through my userns tree?

 security/integrity/evm/evm_crypto.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Mimi Zohar May 3, 2018, 1:43 a.m. UTC | #1
On Wed, 2018-05-02 at 16:49 -0500, Eric W. Biederman wrote:
> From: Seth Forshee <seth.forshee@canonical.com>
> Date: Fri, 22 Dec 2017 15:32:35 +0100
> 
> 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@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: James Morris <james.l.morris@oracle.com>
> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
> Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> ---
> 
> Mimi this patch has been floating around for a while and it appears to
> be the only piece missing from the vfs to make unprivileged mounts safe
> (at least semantically).  Do you want to merge this through your integrity
> tree or should merge this through my userns tree?

Matthew's EVM patches don't conflict with this change, so either way
is fine.

Mimi

> 
>  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 a46fba322340..facf9cdd577d 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -200,7 +200,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
>  	int size;
>  	bool ima_present = false;
> 
> -	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);

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diff mbox

Patch

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index a46fba322340..facf9cdd577d 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -200,7 +200,8 @@  static int evm_calc_hmac_or_hash(struct dentry *dentry,
 	int size;
 	bool ima_present = false;
 
-	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);