integrity: add ima_counts_put (updated)

This patch fixes an imbalance message as reported by J.R. Okajima.
The IMA file counters are incremented in ima_path_check. If the
actual open fails, such as ETXTBSY, decrement the counters to
prevent unnecessary imbalance messages.
Reported-by: J.R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

fs/namei.c

@@ -1761,6 +1761,10 @@ struct file *do_filp_open(int dfd, const char *pathname,
 			goto exit;
 		}
 		filp = nameidata_to_filp(&nd, open_flag);
+		if (IS_ERR(filp))
+			ima_counts_put(&nd.path,
+				       acc_mode & (MAY_READ | MAY_WRITE |
+						   MAY_EXEC));
 		mnt_drop_write(nd.path.mnt);
 		if (nd.root.mnt)
 			path_put(&nd.root);
@@ -1817,6 +1821,9 @@ struct file *do_filp_open(int dfd, const char *pathname,
 		goto exit;
 	}
 	filp = nameidata_to_filp(&nd, open_flag);
+	if (IS_ERR(filp))
+		ima_counts_put(&nd.path,
+			       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC));
 	/*
 	 * It is now safe to drop the mnt write
 	 * because the filp has had a write taken

include/linux/ima.h

@@ -24,6 +24,7 @@ extern int ima_path_check(struct path *path, int mask, int update_counts);
 extern void ima_file_free(struct file *file);
 extern int ima_file_mmap(struct file *file, unsigned long prot);
 extern void ima_counts_get(struct file *file);
+extern void ima_counts_put(struct path *path, int mask);
 
 #else
 static inline int ima_bprm_check(struct linux_binprm *bprm)
@@ -60,5 +61,10 @@ static inline void ima_counts_get(struct file *file)
 {
 	return;
 }
+
+static inline void ima_counts_put(struct path *path, int mask)
+{
+	return;
+}
 #endif /* CONFIG_IMA_H */
 #endif /* _LINUX_IMA_H */

security/integrity/ima/ima_main.c

@@ -238,7 +238,34 @@ static int process_measurement(struct file *file, const unsigned char *filename,
 }
 
 /*
- * ima_opens_get - increment file counts
+ * ima_counts_put - decrement file counts
+ *
+ * File counts are incremented in ima_path_check. On file open
+ * error, such as ETXTBSY, decrement the counts to prevent
+ * unnecessary imbalance messages.
+ */
+void ima_counts_put(struct path *path, int mask)
+{
+	struct inode *inode = path->dentry->d_inode;
+	struct ima_iint_cache *iint;
+
+	if (!ima_initialized || !S_ISREG(inode->i_mode))
+		return;
+	iint = ima_iint_find_insert_get(inode);
+	if (!iint)
+		return;
+
+	mutex_lock(&iint->mutex);
+	iint->opencount--;
+	if ((mask & MAY_WRITE) || (mask == 0))
+		iint->writecount--;
+	else if (mask & (MAY_READ | MAY_EXEC))
+		iint->readcount--;
+	mutex_unlock(&iint->mutex);
+}
+
+/*
+ * ima_counts_get - increment file counts
  *
  * - for IPC shm and shmat file.
  * - for nfsd exported files.