netdev - [PATCH bpf-next] bpf: Use hlist_add_head_rcu when linking to local

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Date:   Wed, 16 Sep 2020 13:44:53 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     <bpf@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
        <netdev@...r.kernel.org>
Subject: [PATCH bpf-next] bpf: Use hlist_add_head_rcu when linking to local_storage

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

This part of the code has recently been refactored in bpf-next
and this patch makes changes to the new file "bpf_local_storage.c".
Instead of using the original offending commit in the Fixes tag,
the commit that created the file "bpf_local_storage.c" is used.

A separate fix has been provided to the bpf tree.

Fixes: 450af8d0f6be ("bpf: Split bpf_local_storage to bpf_sk_storage")
Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/bpf_local_storage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index ffa7d11fc2bd..5d3a7af9ba9b 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -159,7 +159,7 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
 				   struct bpf_local_storage_elem *selem)
 {
 	RCU_INIT_POINTER(selem->local_storage, local_storage);
-	hlist_add_head(&selem->snode, &local_storage->list);
+	hlist_add_head_rcu(&selem->snode, &local_storage->list);
 }
 
 void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
-- 
2.24.1