Re: [PATCH v3 2/3] ima: Return int in the functions to measure a buffer

Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> · Tue, 6 Jul 2021 12:21:04 -0700

On 7/5/2021 2:09 AM, Roberto Sassu wrote:
ima_measure_critical_data() and process_buffer_measurement() currently
don't return a result. A caller wouldn't be able to know whether those
functions were executed successfully.

This patch modifies the return type from void to int, and returns 0 if the
buffer has been successfully measured, a negative value otherwise.

Also, this patch does not modify the behavior of existing callers by
processing the returned value. For those, the return value is ignored.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
  include/linux/ima.h               | 15 +++++++-----
  security/integrity/ima/ima.h      | 10 ++++----
  security/integrity/ima/ima_main.c | 40 ++++++++++++++++++-------------
  3 files changed, 37 insertions(+), 28 deletions(-)

Reviewed-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>

 -lakshmi

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 81e830d01ced..60492263aa64 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -35,10 +35,10 @@ extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
  extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
  extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
  extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
-extern void ima_measure_critical_data(const char *event_label,
-				      const char *event_name,
-				      const void *buf, size_t buf_len,
-				      bool hash);
+extern int ima_measure_critical_data(const char *event_label,
+				     const char *event_name,
+				     const void *buf, size_t buf_len,
+				     bool hash);
  
  #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
  extern void ima_appraise_parse_cmdline(void);
@@ -144,10 +144,13 @@ static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size
  
  static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
  
-static inline void ima_measure_critical_data(const char *event_label,
+static inline int ima_measure_critical_data(const char *event_label,
  					     const char *event_name,
  					     const void *buf, size_t buf_len,
-					     bool hash) {}
+					     bool hash)
+{
+	return -ENOENT;
+}
  
  #endif /* CONFIG_IMA */
  
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index f0e448ed1f9f..03db221324c3 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -264,11 +264,11 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
  			   struct evm_ima_xattr_data *xattr_value,
  			   int xattr_len, const struct modsig *modsig, int pcr,
  			   struct ima_template_desc *template_desc);
-void process_buffer_measurement(struct user_namespace *mnt_userns,
-				struct inode *inode, const void *buf, int size,
-				const char *eventname, enum ima_hooks func,
-				int pcr, const char *func_data,
-				bool buf_hash);
+int process_buffer_measurement(struct user_namespace *mnt_userns,
+			       struct inode *inode, const void *buf, int size,
+			       const char *eventname, enum ima_hooks func,
+			       int pcr, const char *func_data,
+			       bool buf_hash);
  void ima_audit_measurement(struct integrity_iint_cache *iint,
  			   const unsigned char *filename);
  int ima_alloc_init_template(struct ima_event_data *event_data,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 8ef1fa357e0c..b512c06d8ee1 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -827,7 +827,7 @@ int ima_post_load_data(char *buf, loff_t size,
  	return 0;
  }
  
-/*
+/**
   * process_buffer_measurement - Measure the buffer or the buffer data hash
   * @mnt_userns:	user namespace of the mount the inode was found from
   * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
@@ -840,12 +840,15 @@ int ima_post_load_data(char *buf, loff_t size,
   * @buf_hash: measure buffer data hash
   *
   * Based on policy, either the buffer data or buffer data hash is measured
+ *
+ * Return: 0 if the buffer has been successfully measured, a negative value
+ * otherwise.
   */
-void process_buffer_measurement(struct user_namespace *mnt_userns,
-				struct inode *inode, const void *buf, int size,
-				const char *eventname, enum ima_hooks func,
-				int pcr, const char *func_data,
-				bool buf_hash)
+int process_buffer_measurement(struct user_namespace *mnt_userns,
+			       struct inode *inode, const void *buf, int size,
+			       const char *eventname, enum ima_hooks func,
+			       int pcr, const char *func_data,
+			       bool buf_hash)
  {
  	int ret = 0;
  	const char *audit_cause = "ENOMEM";
@@ -867,7 +870,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
  	u32 secid;
  
  	if (!ima_policy_flag)
-		return;
+		return -ENOENT;
  
  	template = ima_template_desc_buf();
  	if (!template) {
@@ -889,7 +892,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
  					secid, 0, func, &pcr, &template,
  					func_data);
  		if (!(action & IMA_MEASURE))
-			return;
+			return -ENOENT;
  	}
  
  	if (!pcr)
@@ -937,7 +940,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
  					func_measure_str(func),
  					audit_cause, ret, 0, ret);
  
-	return;
+	return ret;
  }
  
  /**
@@ -977,18 +980,21 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
   * and extend the pcr.  Examples of critical data could be various data
   * structures, policies, and states stored in kernel memory that can
   * impact the integrity of the system.
+ *
+ * Return: 0 if the buffer has been successfully measured, a negative value
+ * otherwise.
   */
-void ima_measure_critical_data(const char *event_label,
-			       const char *event_name,
-			       const void *buf, size_t buf_len,
-			       bool hash)
+int ima_measure_critical_data(const char *event_label,
+			      const char *event_name,
+			      const void *buf, size_t buf_len,
+			      bool hash)
  {
  	if (!event_name || !event_label || !buf || !buf_len)
-		return;
+		return -ENOPARAM;
  
-	process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, event_name,
-				   CRITICAL_DATA, 0, event_label,
-				   hash);
+	return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
+					  event_name, CRITICAL_DATA, 0,
+					  event_label, hash);
  }
  
  static int __init init_ima(void)







