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    Subject[PATCH 5.15 116/917] mctp: handle the struct sockaddr_mctp padding fields
    Date
    From: Eugene Syromiatnikov <esyr@redhat.com>

    commit 1e4b50f06d970d8da3474d2a0354450416710bda upstream.

    In order to have the padding fields actually usable in the future,
    there have to be checks that user space doesn't supply non-zero garbage
    there. It is also worth setting these padding fields to zero, unless
    it is known that they have been already zeroed.

    Cc: stable@vger.kernel.org # v5.15
    Fixes: 5a20dd46b8b84593 ("mctp: Be explicit about struct sockaddr_mctp padding")
    Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
    Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/mctp/af_mctp.c | 13 +++++++++++++
    1 file changed, 13 insertions(+)

    --- a/net/mctp/af_mctp.c
    +++ b/net/mctp/af_mctp.c
    @@ -30,6 +30,12 @@ static int mctp_release(struct socket *s
    return 0;
    }

    +/* Generic sockaddr checks, padding checks only so far */
    +static bool mctp_sockaddr_is_ok(const struct sockaddr_mctp *addr)
    +{
    + return !addr->__smctp_pad0 && !addr->__smctp_pad1;
    +}
    +
    static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
    {
    struct sock *sk = sock->sk;
    @@ -49,6 +55,9 @@ static int mctp_bind(struct socket *sock
    /* it's a valid sockaddr for MCTP, cast and do protocol checks */
    smctp = (struct sockaddr_mctp *)addr;

    + if (!mctp_sockaddr_is_ok(smctp))
    + return -EINVAL;
    +
    lock_sock(sk);

    /* TODO: allow rebind */
    @@ -83,6 +92,8 @@ static int mctp_sendmsg(struct socket *s
    return -EINVAL;
    if (addr->smctp_family != AF_MCTP)
    return -EINVAL;
    + if (!mctp_sockaddr_is_ok(addr))
    + return -EINVAL;
    if (addr->smctp_tag & ~(MCTP_TAG_MASK | MCTP_TAG_OWNER))
    return -EINVAL;

    @@ -172,11 +183,13 @@ static int mctp_recvmsg(struct socket *s

    addr = msg->msg_name;
    addr->smctp_family = AF_MCTP;
    + addr->__smctp_pad0 = 0;
    addr->smctp_network = cb->net;
    addr->smctp_addr.s_addr = hdr->src;
    addr->smctp_type = type;
    addr->smctp_tag = hdr->flags_seq_tag &
    (MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO);
    + addr->__smctp_pad1 = 0;
    msg->msg_namelen = sizeof(*addr);
    }


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