[PATCH] audit: fix a memleak caused by auditing load module

[Li RongQing]

we should always free context->module.name, since it will be
allocated unconditionally and audit_log_start() can fail with
other reasons, and audit_log_exit maybe not called

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 <zhangy...@baidu.com>
Signed-off-by: Li RongQing <lirongq...@baidu.com>
---
 kernel/auditsc.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b2d1f043f..2bd80375f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1186,8 +1186,13 @@ static void show_special(struct audit_context *context, 
int *call_panic)
        int i;
 
        ab = audit_log_start(context, GFP_KERNEL, context->type);
-       if (!ab)
+       if (!ab) {
+               if (context->type == AUDIT_KERN_MODULE) {
+                       kfree(context->module.name);
+                       context->module.name = NULL;
+               }
                return;
+       }
 
        switch (context->type) {
        case AUDIT_SOCKETCALL: {
@@ -1354,8 +1359,15 @@ static void audit_log_exit(struct audit_context 
*context, struct task_struct *ts
        context->personality = tsk->personality;
 
        ab = audit_log_start(context, GFP_KERNEL, AUDIT_SYSCALL);
-       if (!ab)
+
+       if (!ab) {
+               if (context->type == AUDIT_KERN_MODULE) {
+                       kfree(context->module.name);
+                       context->module.name = NULL;
+               }
                return;         /* audit_panic has been called */
+       }
+
        audit_log_format(ab, "arch=%x syscall=%d",
                         context->arch, context->major);
        if (context->personality != PER_LINUX)
@@ -1576,6 +1588,12 @@ void __audit_syscall_exit(int success, long return_code)
 
        if (context->in_syscall && context->current_state == 
AUDIT_RECORD_CONTEXT)
                audit_log_exit(context, current);
+       else {
+               if (context->type == AUDIT_KERN_MODULE) {
+                       kfree(context->module.name);
+                       context->module.name = NULL;
+               }
+       }
 
        context->in_syscall = 0;
        context->prio = context->state == AUDIT_RECORD_CONTEXT ? ~0ULL : 0;
-- 
2.16.2