IMA: use unsigned int instead of long for counters

Currently IMA uses 2 longs in struct inode.  To save space (and as it
seems impossible to overflow 32 bits) we switch these to unsigned int.
The switch to unsigned does require slightly different checks for
underflow, but it isn't complex.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/integrity/ima/ima.h

@@ -106,8 +106,8 @@ struct ima_iint_cache {
 	unsigned long flags;
 	u8 digest[IMA_DIGEST_SIZE];
 	struct mutex mutex;	/* protects: version, flags, digest */
-	long readcount;		/* measured files readcount */
-	long writecount;	/* measured files writecount */
+	unsigned int readcount;	/* measured files readcount */
+	unsigned int writecount;/* measured files writecount */
 	struct kref refcount;	/* ima_iint_cache reference count */
 };
 

security/integrity/ima/ima_iint.c

@@ -125,12 +125,12 @@ void iint_free(struct kref *kref)
 	iint->version = 0;
 	iint->flags = 0UL;
 	if (iint->readcount != 0) {
-		printk(KERN_INFO "%s: readcount: %ld\n", __func__,
+		printk(KERN_INFO "%s: readcount: %u\n", __func__,
 		       iint->readcount);
 		iint->readcount = 0;
 	}
 	if (iint->writecount != 0) {
-		printk(KERN_INFO "%s: writecount: %ld\n", __func__,
+		printk(KERN_INFO "%s: writecount: %u\n", __func__,
 		       iint->writecount);
 		iint->writecount = 0;
 	}

security/integrity/ima/ima_main.c

@@ -178,22 +178,27 @@ static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
 			   struct file *file)
 {
 	mode_t mode = file->f_mode;
+	bool dump = false;
+
 	BUG_ON(!mutex_is_locked(&iint->mutex));
 
-	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
+		if (unlikely(iint->readcount == 0))
+			dump = true;
 		iint->readcount--;
+	}
 	if (mode & FMODE_WRITE) {
+		if (unlikely(iint->writecount == 0))
+			dump = true;
 		iint->writecount--;
 		if (iint->writecount == 0) {
 			if (iint->version != inode->i_version)
 				iint->flags &= ~IMA_MEASURED;
 		}
 	}
 
-	if (((iint->readcount < 0) ||
-	     (iint->writecount < 0)) &&
-	    !ima_limit_imbalance(file)) {
-		printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld)\n",
+	if (dump && !ima_limit_imbalance(file)) {
+		printk(KERN_INFO "%s: open/free imbalance (r:%u w:%u)\n",
 		       __func__, iint->readcount, iint->writecount);
 		dump_stack();
 	}