ima: kexec: silence RCU list traversal warning

The ima_measurements list is append-only and doesn't require
rcu_read_lock() protection. However, lockdep issues a warning when
traversing RCU lists without the read lock:

  security/integrity/ima/ima_kexec.c:40 RCU-list traversed in non-reader section!!

Fix this by using the variant of list_for_each_entry_rcu() with the last
argument set to true. This tells the RCU subsystem that traversing this
append-only list without the read lock is intentional and safe.

This change silences the lockdep warning while maintaining the correct
semantics for the append-only list traversal.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 52e00332defed39774c9e23e045f1377cfa30d0c..9d45f4d26f731658a79b94b9f95f4dcc4dcb6325 100644 (file)
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -37,7 +37,8 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 
        memset(&khdr, 0, sizeof(khdr));
        khdr.version = 1;
-       list_for_each_entry_rcu(qe, &ima_measurements, later) {
+       /* This is an append-only list, no need to hold the RCU read lock */
+       list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
                if (file.count < file.size) {
                        khdr.count++;
                        ima_measurements_show(&file, qe);