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    Subject[PATCH 5.18 468/879] sctp: read sk->sk_bound_dev_if once in sctp_rcv()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit a20ea298071f46effa3aaf965bf9bb34c901db3f ]

    sctp_rcv() reads sk->sk_bound_dev_if twice while the socket
    is not locked. Another cpu could change this field under us.

    Fixes: 0fd9a65a76e8 ("[SCTP] Support SO_BINDTODEVICE socket option on incoming packets.")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Neil Horman <nhorman@tuxdriver.com>
    Cc: Vlad Yasevich <vyasevich@gmail.com>
    Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/sctp/input.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/net/sctp/input.c b/net/sctp/input.c
    index 90e12bafdd48..4f43afa8678f 100644
    --- a/net/sctp/input.c
    +++ b/net/sctp/input.c
    @@ -92,6 +92,7 @@ int sctp_rcv(struct sk_buff *skb)
    struct sctp_chunk *chunk;
    union sctp_addr src;
    union sctp_addr dest;
    + int bound_dev_if;
    int family;
    struct sctp_af *af;
    struct net *net = dev_net(skb->dev);
    @@ -169,7 +170,8 @@ int sctp_rcv(struct sk_buff *skb)
    * If a frame arrives on an interface and the receiving socket is
    * bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
    */
    - if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb))) {
    + bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
    + if (bound_dev_if && (bound_dev_if != af->skb_iif(skb))) {
    if (transport) {
    sctp_transport_put(transport);
    asoc = NULL;
    --
    2.35.1


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