linux-kernel - Re: [PATCH v2 1/2] evm: fix security.evm for a file with IMA signature

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Message-ID: <7jzx432acnp7mrma7om5ccvrc3ucvm5psscst62bcl5t5yklh7@yxhcvmrgbgli>
Date: Mon, 1 Dec 2025 11:15:32 +0800
From: Coiby Xu <coxu@...hat.com>
To: linux-integrity@...r.kernel.org, Mimi Zohar <zohar@...ux.ibm.com>
Cc: Roberto Sassu <roberto.sassu@...wei.com>, 
	Dmitry Kasatkin <dmitry.kasatkin@...il.com>, Eric Snowberg <eric.snowberg@...cle.com>, 
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
	"Serge E. Hallyn" <serge@...lyn.com>, open list <linux-kernel@...r.kernel.org>, 
	"open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] evm: fix security.evm for a file with IMA
 signature


On Tue, Sep 30, 2025 at 10:26:56AM +0800, Coiby Xu wrote:
>When both IMA and EVM fix modes are enabled, accessing a file with IMA
>signature but missing EVM HMAC won't cause security.evm to be fixed.
>
>Add a function evm_fix_hmac which will be explicitly called to fix EVM
>HMAC for this case.
>
>Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
>Signed-off-by: Coiby Xu <coxu@...hat.com>
>---
> include/linux/evm.h                   |  8 ++++++++
> security/integrity/evm/evm_main.c     | 28 +++++++++++++++++++++++++++
> security/integrity/ima/ima_appraise.c |  5 +++++
> 3 files changed, 41 insertions(+)
>
>diff --git a/include/linux/evm.h b/include/linux/evm.h
>index ddece4a6b25d..913f4573b203 100644
>--- a/include/linux/evm.h
>+++ b/include/linux/evm.h
>@@ -18,6 +18,8 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
> 					     const char *xattr_name,
> 					     void *xattr_value,
> 					     size_t xattr_value_len);
>+int evm_fix_hmac(struct dentry *dentry, const char *xattr_name,
>+		 const char *xattr_value, size_t xattr_value_len);
> int evm_inode_init_security(struct inode *inode, struct inode *dir,
> 			    const struct qstr *qstr, struct xattr *xattrs,
> 			    int *xattr_count);
>@@ -51,6 +53,12 @@ static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
> {
> 	return INTEGRITY_UNKNOWN;
> }
>+
>+static inline int evm_fix_hmac(struct dentry *dentry, const char *xattr_name,
>+			       const char *xattr_value, size_t xattr_value_len)
>+{
>+	return -EOPNOTSUPP;
>+}
> #endif
>
> static inline int evm_inode_init_security(struct inode *inode, struct inode *dir,
>diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
>index 0add782e73ba..1b3edc6d26e9 100644
>--- a/security/integrity/evm/evm_main.c
>+++ b/security/integrity/evm/evm_main.c
>@@ -787,6 +787,34 @@ bool evm_revalidate_status(const char *xattr_name)
> 	return true;
> }
>
>+/**
>+ * evm_fix_hmac - Calculate the HMAC and add it to security.evm for fix mode
>+ * @dentry: pointer to the affected dentry which doesn't yet have security.evm
>+ *          xattr
>+ * @xattr_name: pointer to the affected extended attribute name
>+ * @xattr_value: pointer to the new extended attribute value
>+ * @xattr_value_len: pointer to the new extended attribute value length
>+ *
>+ * Expects to be called with i_mutex locked.
>+ *
>+ * Return: 0 on success, -EPERM/-ENOMEM/-EOPNOTSUPP on failure
>+ */
>+int evm_fix_hmac(struct dentry *dentry, const char *xattr_name,
>+		 const char *xattr_value, size_t xattr_value_len)
>+
>+{
>+	if (!evm_fixmode || !evm_revalidate_status((xattr_name)))
>+		return -EPERM;
>+
>+	if (!(evm_initialized & EVM_INIT_HMAC))
>+		return -EPERM;
>+
>+	if (is_unsupported_hmac_fs(dentry))
>+		return -EOPNOTSUPP;
>+
>+	return evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
>+}
>+
> /**
>  * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
>  * @dentry: pointer to the affected dentry
>diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
>index f435eff4667f..f48ef5ec185e 100644
>--- a/security/integrity/ima/ima_appraise.c
>+++ b/security/integrity/ima/ima_appraise.c
>@@ -601,6 +601,11 @@ int ima_appraise_measurement(enum ima_hooks func, struct ima_iint_cache *iint,
> 		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
> 			if (!ima_fix_xattr(dentry, iint))
> 				status = INTEGRITY_PASS;
>+		} else if (status == INTEGRITY_NOLABEL) {
>+			if (!evm_fix_hmac(dentry, XATTR_NAME_IMA,
>+					  (const char *)xattr_value,
>+					  xattr_len))
>+				status = INTEGRITY_PASS;
> 		}
>
> 		/*
>
>base-commit: e129e479f2e444eaccd822717d418119d39d3d5c
>-- 
>2.51.0
>

Hi Mimi,

I think this patch set just fell off the radar. Can you take a look at
it when time permits? Thanks! Btw, the patch set is still applicable to
current next-integrity tree Linus and main tree.


-- 
Best regards,
Coiby