[PATCH bpf] bpf: Use hlist_add_head_rcu when linking to sk_storage

[Martin KaFai Lau <kafai@xxxxxx>]

The sk_storage->list will be traversed by rcu reader in parallel.
Thus, hlist_add_head_rcu() is needed in __selem_link_sk().  This
patch fixes it.

This part of the code has recently been refactored in bpf-next.
A separate fix will be provided for the bpf-next tree.

Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
 net/core/bpf_sk_storage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index b988f48153a4..d4d2a56e9d4a 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -219,7 +219,7 @@ static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
 			    struct bpf_sk_storage_elem *selem)
 {
 	RCU_INIT_POINTER(selem->sk_storage, sk_storage);
-	hlist_add_head(&selem->snode, &sk_storage->list);
+	hlist_add_head_rcu(&selem->snode, &sk_storage->list);
 }
 
 static void selem_unlink_map(struct bpf_sk_storage_elem *selem)
-- 
2.24.1