Re: [PATCH][v2] audit: fix a memleak caused by auditing load module
On Wed, Mar 6, 2019 at 2:33 AM Li RongQing <lirongqing(a)baidu.com> wrote:
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 released
so free module.name in audit_free_context and audit exit syscall
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(a)baidu.com>
Signed-off-by: Li RongQing <lirongqing(a)baidu.com>
---
kernel/auditsc.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b2d1f043f..07728b07a 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -964,6 +964,9 @@ int audit_alloc(struct task_struct *tsk)
static inline void audit_free_context(struct audit_context *context)
{
+ if (context->type == AUDIT_KERN_MODULE)
+ kfree(context->module.name);
+
audit_free_names(context);
unroll_tree_refs(context, NULL, 0);
free_tree_refs(context);
@@ -1282,6 +1285,8 @@ static void show_special(struct audit_context *context, int
*call_panic)
if (context->module.name) {
audit_log_untrustedstring(ab, context->module.name);
kfree(context->module.name);
+ context->module.name = NULL;
+ context->type = 0;
I think we can get rid of the kfree() and other cleanup here, yes?
The show_special() function is only going to end up being called from
__audit_free() or __audit_syscall_exit() and both functions appear to
cleanup the audit_context struct correctly (assuming we fixup the
__audit_syscall_exit() below).
} else
audit_log_format(ab, "(null)");
@@ -1583,6 +1588,11 @@ void __audit_syscall_exit(int success, long return_code)
if (!list_empty(&context->killed_trees))
audit_kill_trees(&context->killed_trees);
+ if (context->type == AUDIT_KERN_MODULE) {
+ kfree(context->module.name);
+ context->module.name = NULL;
+ }
Since we have to worry about free'ing the memory in places other than
audit_free_context(), let's create a helper function similar to
audit_free_aux() and use that when we need to free module.name. For
example:
static inline void audit_free_module(struct audit_context *context)
{
if (context-type == AUDIT_KERN_MODULE) {
kfree(context->module.name);
context->module.name = NULL;
}
}
audit_free_names(context);
unroll_tree_refs(context, NULL, 0);
audit_free_aux(context);
--
2.16.2
--
paul moore
www.paul-moore.com