netdev - [PATCH bpf-next 08/19] bpf: Disable migration when cloning sock storage

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Message-Id: <20250106081900.1665573-9-houtao@huaweicloud.com>
Date: Mon,  6 Jan 2025 16:18:49 +0800
From: Hou Tao <houtao@...weicloud.com>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Hao Luo <haoluo@...gle.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Daniel Borkmann <daniel@...earbox.net>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	houtao1@...wei.com,
	xukuohai@...wei.com
Subject: [PATCH bpf-next 08/19] bpf: Disable migration when cloning sock storage

From: Hou Tao <houtao1@...wei.com>

bpf_sk_storage_clone() will call bpf_selem_free() to free the clone
element when the allocation of new sock storage fails. bpf_selem_free()
will call check_and_free_fields() to free the special fields in the
element. Since the allocated element is not visible to bpf syscall or
bpf program when bpf_local_storage_alloc() fails, these special fields
in the element must be all zero when invoking bpf_selem_free().

To be uniform with other callers of bpf_selem_free(), disabling
migration when cloning sock storage. Adding migrate_{disable|enable}
pair also benefits the potential switching from kzalloc to bpf memory
allocator for sock storage.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 net/core/bpf_sk_storage.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index aa536ecd5d39..7d41cde1bcca 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -161,6 +161,7 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
 
 	RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
 
+	migrate_disable();
 	rcu_read_lock();
 	sk_storage = rcu_dereference(sk->sk_bpf_storage);
 
@@ -213,6 +214,7 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
 
 out:
 	rcu_read_unlock();
+	migrate_enable();
 
 	/* In case of an error, don't free anything explicitly here, the
 	 * caller is responsible to call bpf_sk_storage_free.
-- 
2.29.2