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sunrpc: xprtsock: annotate shared socket callbacks with READ_ONCE/WRITE_ONCE

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xprtsock replaces and restores sk->sk_data_ready and
sk->sk_write_space on live sockets with plain stores, and
xs_udp_do_set_buffer_size() invokes sk->sk_write_space via a plain
load. These callback pointers are shared with generic socket and
protocol paths that may read or invoke them concurrently, so xprtsock
needs the same READ_ONCE()/WRITE_ONCE() callback visibility contract
that the validated 4022 family applied elsewhere.

When SUNRPC takes over an AF_LOCAL, UDP, or TCP socket and later
restores the lower-socket callbacks during teardown, another CPU may
still hold an earlier callback snapshot. The plain replace/restore
pattern leaves the same visibility hole as the validated 4022 family,
so a stale snapshot can still invoke xs_data_ready() or
xs_udp_write_space() after the live callback fields have already been
restored to the lower-socket handlers.

Use WRITE_ONCE() for the shared sk_data_ready and sk_write_space
stores in xs_local_finish_connecting(), xs_udp_finish_connecting(),
xs_tcp_finish_connecting(), and xs_restore_old_callbacks(). Use
READ_ONCE() for the direct sk_write_space invocation in
xs_udp_do_set_buffer_size(). This matches the required callback
visibility contract while leaving adjacent sk_state_change and
sk_error_report handling unchanged.

Fixes: a246b0105b ("[PATCH] RPC: introduce client-side transport switch")
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Runyu Xiao 2026-06-11 13:35:56 +08:00 committed by Trond Myklebust
parent fd22370226
commit 33930840b5
1 changed files with 11 additions and 9 deletions
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20
net/sunrpc/xprtsock.c
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@ -1202,9 +1202,9 @@ static void xs_save_old_callbacks(struct sock_xprt *transport, struct sock *sk)
static void xs_restore_old_callbacks(struct sock_xprt *transport, struct sock *sk)
{
sk->sk_data_ready = transport->old_data_ready;
WRITE_ONCE(sk->sk_data_ready, transport->old_data_ready);
sk->sk_state_change = transport->old_state_change;
sk->sk_write_space = transport->old_write_space;
WRITE_ONCE(sk->sk_write_space, transport->old_write_space);
sk->sk_error_report = transport->old_error_report;
}
@ -1664,6 +1664,7 @@ static void xs_udp_do_set_buffer_size(struct rpc_xprt *xprt)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
struct sock *sk = transport->inet;
void (*write_space)(struct sock *sock);
if (transport->rcvsize) {
sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
@ -1672,7 +1673,8 @@ static void xs_udp_do_set_buffer_size(struct rpc_xprt *xprt)
if (transport->sndsize) {
sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
sk->sk_sndbuf = transport->sndsize * xprt->max_reqs * 2;
sk->sk_write_space(sk);
write_space = READ_ONCE(sk->sk_write_space);
write_space(sk);
}
}
@ -1988,8 +1990,8 @@ static int xs_local_finish_connecting(struct rpc_xprt *xprt,
xs_save_old_callbacks(transport, sk);
sk->sk_user_data = xprt;
sk->sk_data_ready = xs_data_ready;
sk->sk_write_space = xs_udp_write_space;
WRITE_ONCE(sk->sk_data_ready, xs_data_ready);
WRITE_ONCE(sk->sk_write_space, xs_udp_write_space);
sk->sk_state_change = xs_local_state_change;
sk->sk_error_report = xs_error_report;
sk->sk_use_task_frag = false;
@ -2191,8 +2193,8 @@ static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
xs_save_old_callbacks(transport, sk);
sk->sk_user_data = xprt;
sk->sk_data_ready = xs_data_ready;
sk->sk_write_space = xs_udp_write_space;
WRITE_ONCE(sk->sk_data_ready, xs_data_ready);
WRITE_ONCE(sk->sk_write_space, xs_udp_write_space);
sk->sk_use_task_frag = false;
xprt_set_connected(xprt);
@ -2378,9 +2380,9 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
xs_save_old_callbacks(transport, sk);
sk->sk_user_data = xprt;
sk->sk_data_ready = xs_data_ready;
WRITE_ONCE(sk->sk_data_ready, xs_data_ready);
sk->sk_state_change = xs_tcp_state_change;
sk->sk_write_space = xs_tcp_write_space;
WRITE_ONCE(sk->sk_write_space, xs_tcp_write_space);
sk->sk_error_report = xs_error_report;
sk->sk_use_task_frag = false;