From d38a65125f93b2fbd17cd37ccc5ec0f0b799cc55 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 10 Aug 2017 16:53:00 +0200 Subject: [PATCH] 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: 019a316992ee ("rtnetlink: add reference counting to prevent module unload while dump is in progress") Reported-by: Sabrina Dubroca Reported-by: kernel test robot Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/core/rtnetlink.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 087f2434813a..59eda6952bc9 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -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");