linux-kernel - [RFC][PATCH 7/9] evm: make rootfs a special case

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Message-Id: <1420663980-20842-8-git-send-email-zohar@linux.vnet.ibm.com>
Date:	Wed,  7 Jan 2015 15:52:58 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	initramfs <initramfs@...r.kernel.org>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-ima-devel@...ts.sourceforge.net,
	linux-security-module <linux-security-module@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [RFC][PATCH 7/9] evm: make rootfs a special case

Both the EVM HMAC and signature xattr formats are file system
specific and can not be copied from one filesystem to another.

EVM differentiates files without any xattrs (INTEGRITY_UNKNOWN)
from those having protected xattrs (INTEGRITY_NOLABEL).  This
patch treats the rootfs filesystem as a special case, returning
INTEGRITY_UNKNOWN.

Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
---
 security/integrity/evm/evm_main.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index b392fe6..9c71af7 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -128,11 +128,16 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 	if (rc <= 0) {
 		evm_status = INTEGRITY_FAIL;
 		if (rc == -ENODATA) {
+			struct super_block *sb = dentry->d_inode->i_sb;
+
 			rc = evm_find_protected_xattrs(dentry);
-			if (rc > 0)
-				evm_status = INTEGRITY_NOLABEL;
-			else if (rc == 0)
+			if (rc == 0)
 				evm_status = INTEGRITY_NOXATTRS; /* new file */
+			else if (rc > 0 && sb->s_magic == TMPFS_MAGIC
+				 && strcmp(sb->s_id, "rootfs") == 0)
+				evm_status = INTEGRITY_UNKNOWN;
+			else if (rc > 0)
+				evm_status = INTEGRITY_NOLABEL;
 		} else if (rc == -EOPNOTSUPP) {
 			evm_status = INTEGRITY_UNKNOWN;
 		}
-- 
1.8.1.4

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