[PATCH 3.17 058/319] evm: properly handle INTEGRITY_NOXATTRS EVM status

[Greg Kroah-Hartman]

3.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Kasatkin <d.kasatkin@xxxxxxxxxxx>

commit 3dcbad52cf18c3c379e96b992d22815439ebbe53 upstream.

Unless an LSM labels a file during d_instantiate(), newly created
files are not labeled with an initial security.evm xattr, until
the file closes.  EVM, before allowing a protected, security xattr
to be written, verifies the existing 'security.evm' value is good.
For newly created files without a security.evm label, this
verification prevents writing any protected, security xattrs,
until the file closes.

Following is the example when this happens:
fd = open("foo", O_CREAT | O_WRONLY, 0644);
setxattr("foo", "security.SMACK64", value, sizeof(value), 0);
close(fd);

While INTEGRITY_NOXATTRS status is handled in other places, such
as evm_inode_setattr(), it does not handle it in all cases in
evm_protect_xattr().  By limiting the use of INTEGRITY_NOXATTRS to
newly created files, we can now allow setting "protected" xattrs.

Changelog:
- limit the use of INTEGRITY_NOXATTRS to IMA identified new files

Signed-off-by: Dmitry Kasatkin <d.kasatkin@xxxxxxxxxxx>
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 security/integrity/evm/evm_main.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -284,6 +284,13 @@ static int evm_protect_xattr(struct dent
 		goto out;
 	}
 	evm_status = evm_verify_current_integrity(dentry);
+	if (evm_status == INTEGRITY_NOXATTRS) {
+		struct integrity_iint_cache *iint;
+
+		iint = integrity_iint_find(dentry->d_inode);
+		if (iint && (iint->flags & IMA_NEW_FILE))
+			return 0;
+	}
 out:
 	if (evm_status != INTEGRITY_PASS)
 		integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,


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