IMA: maintain i_readcount in the VFS layer

ima_counts_get() updated the readcount and invalidated the PCR,
as necessary. Only update the i_readcount in the VFS layer.
Move the PCR invalidation checks to ima_file_check(), where it
belongs.

Maintaining the i_readcount in the VFS layer, will allow other
subsystems to use i_readcount.

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Eric Paris <eparis@redhat.com>

fs/file_table.c

@@ -190,7 +190,8 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 		file_take_write(file);
 		WARN_ON(mnt_clone_write(path->mnt));
 	}
-	ima_counts_get(file);
+	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+		i_readcount_inc(path->dentry->d_inode);
 	return file;
 }
 EXPORT_SYMBOL(alloc_file);
@@ -251,6 +252,8 @@ static void __fput(struct file *file)
 	fops_put(file->f_op);
 	put_pid(file->f_owner.pid);
 	file_sb_list_del(file);
+	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+		i_readcount_dec(inode);
 	if (file->f_mode & FMODE_WRITE)
 		drop_file_write_access(file);
 	file->f_path.dentry = NULL;

fs/open.c

@@ -688,7 +688,8 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 		if (error)
 			goto cleanup_all;
 	}
-	ima_counts_get(f);
+	if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+		i_readcount_inc(inode);
 
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 

include/linux/ima.h

@@ -20,7 +20,6 @@ extern void ima_inode_free(struct inode *inode);
 extern int ima_file_check(struct file *file, int mask);
 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);
 
 #else
 static inline int ima_bprm_check(struct linux_binprm *bprm)
@@ -53,10 +52,5 @@ static inline int ima_file_mmap(struct file *file, unsigned long prot)
 	return 0;
 }
 
-static inline void ima_counts_get(struct file *file)
-{
-	return;
-}
-
 #endif /* CONFIG_IMA_H */
 #endif /* _LINUX_IMA_H */

security/integrity/ima/ima_iint.c

@@ -141,8 +141,6 @@ void ima_inode_free(struct inode *inode)
 		printk(KERN_INFO "%s: readcount: %u\n", __func__,
 		       atomic_read(&inode->i_readcount));
 
-	atomic_set(&inode->i_readcount, 0);
-
 	if (!IS_IMA(inode))
 		return;
 

security/integrity/ima/ima_main.c

@@ -86,17 +86,16 @@ out:
 }
 
 /*
- * ima_counts_get - increment file counts
+ * ima_rdwr_violation_check
  *
- * Maintain read/write counters for all files, but only
+ * Only invalidate the PCR for measured files:
- * invalidate the PCR for measured files:
  * 	- Opening a file for write when already open for read,
  *	  results in a time of measure, time of use (ToMToU) error.
  *	- Opening a file for read when already open for write,
  * 	  could result in a file measurement error.
  *
  */
-void ima_counts_get(struct file *file)
+static void ima_rdwr_violation_check(struct file *file)
 {
 	struct dentry *dentry = file->f_path.dentry;
 	struct inode *inode = dentry->d_inode;
@@ -104,13 +103,10 @@ void ima_counts_get(struct file *file)
 	int rc;
 	bool send_tomtou = false, send_writers = false;
 
-	if (!S_ISREG(inode->i_mode))
+	if (!S_ISREG(inode->i_mode) || !ima_initialized)
 		return;
 
-	spin_lock(&inode->i_lock);
+	mutex_lock(&inode->i_mutex);	/* file metadata: permissions, xattr */
-
-	if (!ima_initialized)
-		goto out;
 
 	if (mode & FMODE_WRITE) {
 		if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
@@ -125,11 +121,7 @@ void ima_counts_get(struct file *file)
 	if (atomic_read(&inode->i_writecount) > 0)
 		send_writers = true;
 out:
-	/* remember the vfs deals with i_writecount */
+	mutex_unlock(&inode->i_mutex);
-	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
-		atomic_inc(&inode->i_readcount);
-
-	spin_unlock(&inode->i_lock);
 
 	if (send_tomtou)
 		ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
@@ -158,7 +150,6 @@ static void ima_dec_counts(struct inode *inode, struct file *file)
 			}
 			return;
 		}
-		atomic_dec(&inode->i_readcount);
 	}
 }
 
@@ -203,8 +194,7 @@ static void ima_file_free_noiint(struct inode *inode, struct file *file)
  * ima_file_free - called on __fput()
  * @file: pointer to file structure being freed
  *
- * Flag files that changed, based on i_version;
+ * Flag files that changed, based on i_version
- * and decrement the i_readcount.
  */
 void ima_file_free(struct file *file)
 {
@@ -318,6 +308,7 @@ int ima_file_check(struct file *file, int mask)
 {
 	int rc;
 
+	ima_rdwr_violation_check(file);
 	rc = process_measurement(file, file->f_dentry->d_name.name,
 				 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 				 FILE_CHECK);