[RFC PATCH v2 1/2] ima: limit the number of open-writers integrity violations

[Mimi Zohar]

Limit the number of open-writers integrity violation audit messages
and records in the IMA measurement list emitted when re-opening a
file for read.

Signed-off-by: Mimi Zohar <zo...@linux.ibm.com>
---
 security/integrity/ima/ima.h      |  1 +
 security/integrity/ima/ima_main.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index a4f284bd846c..7f21568544dd 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -182,6 +182,7 @@ struct ima_kexec_hdr {
 #define IMA_CHANGE_ATTR                2
 #define IMA_DIGSIG             3
 #define IMA_MUST_MEASURE       4
+#define IMA_LIMIT_VIOLATIONS   5
 
 /* IMA integrity metadata associated with an inode */
 struct ima_iint_cache {
diff --git a/security/integrity/ima/ima_main.c 
b/security/integrity/ima/ima_main.c
index 28b8b0db6f9b..5091ad931677 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -137,8 +137,16 @@ static void ima_rdwr_violation_check(struct file *file,
        } else {
                if (must_measure)
                        set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
-               if (inode_is_open_for_write(inode) && must_measure)
-                       send_writers = true;
+
+               if (inode_is_open_for_write(inode) && must_measure) {
+                       if (!iint)
+                               iint = ima_iint_find(inode);
+
+                       /* Limit number of open_writers violations */
+                       if (iint && !test_and_set_bit(IMA_LIMIT_VIOLATIONS,
+                                                     &iint->atomic_flags))
+                               send_writers = true;
+               }
        }
 
        if (!send_tomtou && !send_writers)
@@ -167,6 +175,8 @@ static void ima_check_last_writer(struct ima_iint_cache 
*iint,
        if (atomic_read(&inode->i_writecount) == 1) {
                struct kstat stat;
 
+               clear_bit(IMA_LIMIT_VIOLATIONS, &iint->atomic_flags);
+
                update = test_and_clear_bit(IMA_UPDATE_XATTR,
                                            &iint->atomic_flags);
                if ((iint->flags & IMA_NEW_FILE) ||
-- 
2.48.1