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

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Message-Id: <1551784466-15610-1-git-send-email-lirongqing@baidu.com>
Date:   Tue,  5 Mar 2019 19:14:26 +0800
From:   Li RongQing <lirongqing@...du.com>
To:     paul@...l-moore.com, eparis@...hat.com, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH] audit: fix a memleak caused by auditing load module

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 <zhangyu31@...du.com>
Signed-off-by: Li RongQing <lirongqing@...du.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