Subject: [PATCH 05/11] xfrm: fix rcu usage in xfrm_get_type_offload

From: Steffen Klassert <[email-masked]>
Date: Thu, 11 Jan 2018 12:37:40 +0100

From: Sabrina Dubroca <[email-masked]>

request_module can sleep, thus we cannot hold rcu_read_lock() while
calling it. The function also jumps back and takes rcu_read_lock()
again (in xfrm_state_get_afinfo()), resulting in an imbalance.

This codepath is triggered whenever a new offloaded state is created.

Fixes: ffdb5211da1c ("xfrm: Auto-load xfrm offload modules")
Reported-by: [email-masked]
Signed-off-by: Sabrina Dubroca <[email-masked]>
Signed-off-by: Steffen Klassert <[email-masked]>
---
 net/xfrm/xfrm_state.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 1e80f68e2266..429957412633 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -313,13 +313,14 @@ xfrm_get_type_offload(u8 proto, unsigned short family, bool try_load)
 	if ((type && !try_module_get(type->owner)))
 		type = NULL;
 
+	rcu_read_unlock();
+
 	if (!type && try_load) {
 		request_module("xfrm-offload-%d-%d", family, proto);
 		try_load = 0;
 		goto retry;
 	}
 
-	rcu_read_unlock();
 	return type;
 }
 
-- 
2.14.1