Merge tag 'integrity-v6.15' of git://git.kernel.org/pub/scm/linux/ker…

…nel/git/zohar/linux-integrity

Pull ima updates from Mimi Zohar:
 "Two performance improvements, which minimize the number of integrity
  violations"

* tag 'integrity-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
  ima: limit the number of ToMToU integrity violations
  ima: limit the number of open-writers integrity violations

security/integrity/ima/ima.h

@@ -181,7 +181,8 @@ struct ima_kexec_hdr {
 #define IMA_UPDATE_XATTR	1
 #define IMA_CHANGE_ATTR		2
 #define IMA_DIGSIG		3
-#define IMA_MUST_MEASURE	4
+#define IMA_MAY_EMIT_TOMTOU	4
+#define IMA_EMITTED_OPENWRITERS	5
 
 /* IMA integrity metadata associated with an inode */
 struct ima_iint_cache {

security/integrity/ima/ima_main.c

@@ -129,16 +129,22 @@ static void ima_rdwr_violation_check(struct file *file,
 		if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
 			if (!iint)
 				iint = ima_iint_find(inode);
+
 			/* IMA_MEASURE is set from reader side */
-			if (iint && test_bit(IMA_MUST_MEASURE,
-						&iint->atomic_flags))
+			if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU,
+						       &iint->atomic_flags))
 				send_tomtou = true;
 		}
 	} else {
 		if (must_measure)
-			set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
-		if (inode_is_open_for_write(inode) && must_measure)
-			send_writers = true;
+			set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags);
+
+		/* Limit number of open_writers violations */
+		if (inode_is_open_for_write(inode) && must_measure) {
+			if (!test_and_set_bit(IMA_EMITTED_OPENWRITERS,
+					      &iint->atomic_flags))
+				send_writers = true;
+		}
 	}
 
 	if (!send_tomtou && !send_writers)
@@ -167,6 +173,8 @@ static void ima_check_last_writer(struct ima_iint_cache *iint,
 	if (atomic_read(&inode->i_writecount) == 1) {
 		struct kstat stat;
 
+		clear_bit(IMA_EMITTED_OPENWRITERS, &iint->atomic_flags);
+
 		update = test_and_clear_bit(IMA_UPDATE_XATTR,
 					    &iint->atomic_flags);
 		if ((iint->flags & IMA_NEW_FILE) ||