Commit d38a6512 authored Aug 10, 2017 by Florian Westphal Committed by David S. Miller Aug 10, 2017

rtnetlink: init handler refcounts to 1



If using CONFIG_REFCOUNT_FULL=y we get following splat:
 refcount_t: increment on 0; use-after-free.
WARNING: CPU: 0 PID: 304 at lib/refcount.c:152 refcount_inc+0x47/0x50
Call Trace:
 rtnetlink_rcv_msg+0x191/0x260
 ...

This warning is harmless (0 is "no callback running", not "memory
was freed").

Use '1' as the new 'no handler is running' base instead of 0 to avoid
this.

Fixes: 019a3169 ("rtnetlink: add reference counting to prevent module unload while dump is in progress")
Reported-by: Sabrina Dubroca <sdubroca@redhat.com>
Reported-by: kernel test robot <fengguang.wu@intel.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8515ae38

net/core/rtnetlink.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -262,7 +262,7 @@ void rtnl_unregister_all(int protocol)

		synchronize_net();

		while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 0)
		while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 1)
		schedule();
		kfree(handlers);
		}
		@@ -4324,6 +4324,11 @@ static struct pernet_operations rtnetlink_net_ops = {

		void __init rtnetlink_init(void)
		{
		int i;

		for (i = 0; i < ARRAY_SIZE(rtnl_msg_handlers_ref); i++)
		refcount_set(&rtnl_msg_handlers_ref[i], 1);

		if (register_pernet_subsys(&rtnetlink_net_ops))
		panic("rtnetlink_init: cannot initialize rtnetlink\n");

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