[Devel] [PATCH RHEL8 COMMIT] ms/audit: fix a memleak caused by auditing load module

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-80.1.2.vz8.3.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-80.1.2.vz8.3.11
------>
commit 77f73d578c0da6f286f73969e4af12929ee7e268
Author: Li RongQing <lirongqing at baidu.com>
Date:   Thu Mar 7 09:16:24 2019 +0800

    ms/audit: fix a memleak caused by auditing load module
    
    module.name will be allocated unconditionally when auditing load
    module, and audit_log_start() can fail with other reasons, or
    audit_log_exit maybe not called, caused module.name is not freed
    
    so free module.name in audit_free_context and __audit_syscall_exit
    
    unreferenced object 0xffff88af90837d20 (size 8):
      comm "modprobe", pid 1036, jiffies 4294704867 (age 3069.138s)
      hex dump (first 8 bytes):
        69 78 67 62 65 00 ff ff                          ixgbe...
      backtrace:
        [<0000000008da28fe>] __audit_log_kern_module+0x33/0x80
        [<00000000c1491e61>] load_module+0x64f/0x3850
        [<000000007fc9ae3f>] __do_sys_init_module+0x218/0x250
        [<0000000000d4a478>] do_syscall_64+0x117/0x400
        [<000000004924ded8>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
        [<000000007dc331dd>] 0xffffffffffffffff
    
    Fixes: ca86cad7380e3 ("audit: log module name on init_module")
    Signed-off-by: Zhang Yu <zhangyu31 at baidu.com>
    Signed-off-by: Li RongQing <lirongqing at baidu.com>
    [PM: manual merge fixup in __audit_syscall_exit()]
    Signed-off-by: Paul Moore <paul at paul-moore.com>
    
    https://jira.sw.ru/browse/PSBM-104567
    
    (cherry picked from commit 95e0b46fcebd7dbf6850dee96046e4c4ddc7f69c)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 kernel/auditsc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3b4fff24eac8..d16878f20d5d 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -881,6 +881,13 @@ static inline void audit_proctitle_free(struct audit_context *context)
 	context->proctitle.len = 0;
 }
 
+static inline void audit_free_module(struct audit_context *context)
+{
+	if (context->type == AUDIT_KERN_MODULE) {
+		kfree(context->module.name);
+		context->module.name = NULL;
+	}
+}
 static inline void audit_free_names(struct audit_context *context)
 {
 	struct audit_names *n, *next;
@@ -964,6 +971,7 @@ int audit_alloc(struct task_struct *tsk)
 
 static inline void audit_free_context(struct audit_context *context)
 {
+	audit_free_module(context);
 	audit_free_names(context);
 	unroll_tree_refs(context, NULL, 0);
 	free_tree_refs(context);
@@ -1281,7 +1289,6 @@ static void show_special(struct audit_context *context, int *call_panic)
 		audit_log_format(ab, "name=");
 		if (context->module.name) {
 			audit_log_untrustedstring(ab, context->module.name);
-			kfree(context->module.name);
 		} else
 			audit_log_format(ab, "(null)");
 
@@ -1583,6 +1590,7 @@ void __audit_syscall_exit(int success, long return_code)
 	if (!list_empty(&context->killed_trees))
 		audit_kill_trees(&context->killed_trees);
 
+	audit_free_module(context);
 	audit_free_names(context);
 	unroll_tree_refs(context, NULL, 0);
 	audit_free_aux(context);