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>

2 files changed, 8 insertions, 19 deletions

diff --git a/security/integrity/ima/ima_iint.c b/security/integrity/ima/ima_iint.c
index f0053552fd5..68efe3b8d99 100644
--- a/security/integrity/ima/ima_iint.c
+++ b/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;
 
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 6e8cb931b8f..69b4856af4d 100644
--- a/security/integrity/ima/ima_main.c
+++ b/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
- * invalidate the PCR for measured files:
+ * Only 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);
-
-        if (!ima_initialized)
-                goto out;
+        mutex_lock(&inode->i_mutex);    /* file metadata: permissions, xattr */
 
         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 */
-        if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
-                atomic_inc(&inode->i_readcount);
-
-        spin_unlock(&inode->i_lock);
+        mutex_unlock(&inode->i_mutex);
 
         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;
- * and decrement the i_readcount.
+ * Flag files that changed, based on i_version
  */
 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);