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    Subject[PATCH 4.19 600/639] net: add {READ|WRITE}_ONCE() annotations on ->rskq_accept_head
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 60b173ca3d1cd1782bd0096dc17298ec242f6fb1 ]

    reqsk_queue_empty() is called from inet_csk_listen_poll() while
    other cpus might write ->rskq_accept_head value.

    Use {READ|WRITE}_ONCE() to avoid compiler tricks
    and potential KCSAN splats.

    Fixes: fff1f3001cc5 ("tcp: add a spinlock to protect struct request_sock_queue")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/xen/pvcalls-back.c | 2 +-
    include/net/request_sock.h | 4 ++--
    net/ipv4/inet_connection_sock.c | 2 +-
    3 files changed, 4 insertions(+), 4 deletions(-)

    diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
    index d4ea33581ac26..b3fbfed28682f 100644
    --- a/drivers/xen/pvcalls-back.c
    +++ b/drivers/xen/pvcalls-back.c
    @@ -784,7 +784,7 @@ static int pvcalls_back_poll(struct xenbus_device *dev,
    mappass->reqcopy = *req;
    icsk = inet_csk(mappass->sock->sk);
    queue = &icsk->icsk_accept_queue;
    - data = queue->rskq_accept_head != NULL;
    + data = READ_ONCE(queue->rskq_accept_head) != NULL;
    if (data) {
    mappass->reqcopy.cmd = 0;
    ret = 0;
    diff --git a/include/net/request_sock.h b/include/net/request_sock.h
    index 347015515a7de..1653435f18f5c 100644
    --- a/include/net/request_sock.h
    +++ b/include/net/request_sock.h
    @@ -183,7 +183,7 @@ void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,

    static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
    {
    - return queue->rskq_accept_head == NULL;
    + return READ_ONCE(queue->rskq_accept_head) == NULL;
    }

    static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
    @@ -195,7 +195,7 @@ static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue
    req = queue->rskq_accept_head;
    if (req) {
    sk_acceptq_removed(parent);
    - queue->rskq_accept_head = req->dl_next;
    + WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
    if (queue->rskq_accept_head == NULL)
    queue->rskq_accept_tail = NULL;
    }
    diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
    index 636a11c56cf5a..79320858e7196 100644
    --- a/net/ipv4/inet_connection_sock.c
    +++ b/net/ipv4/inet_connection_sock.c
    @@ -937,7 +937,7 @@ struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
    req->sk = child;
    req->dl_next = NULL;
    if (queue->rskq_accept_head == NULL)
    - queue->rskq_accept_head = req;
    + WRITE_ONCE(queue->rskq_accept_head, req);
    else
    queue->rskq_accept_tail->dl_next = req;
    queue->rskq_accept_tail = req;
    --
    2.20.1


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