On Tue, Sep 10, 2019 at 9:19 PM David Laight [off-list ref] wrote:

From: Xin Long

quoted

Sent: 09 September 2019 08:57
Section 7.2 of rfc7829: "Peer Address Thresholds (SCTP_PEER_ADDR_THLDS)
Socket Option" extends 'struct sctp_paddrthlds' with 'spt_pathcpthld'
added to allow a user to change ps_retrans per sock/asoc/transport, as
other 2 paddrthlds: pf_retrans, pathmaxrxt.

Note that ps_retrans is not allowed to be greater than pf_retrans.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 include/uapi/linux/sctp.h |  1 +
 net/sctp/socket.c         | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index a15cc28..dfd81e1 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h

@@ -1069,6 +1069,7 @@ struct sctp_paddrthlds {
      struct sockaddr_storage spt_address;
      __u16 spt_pathmaxrxt;
      __u16 spt_pathpfthld;
+     __u16 spt_pathcpthld;
 };

 /*

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 5e2098b..5b9774d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -3954,6 +3954,9 @@ static int sctp_setsockopt_paddr_thresholds(struct sock *sk,

This code does:
        if (optlen < sizeof(struct sctp_paddrthlds))
                return -EINVAL;

here will become:

        if (optlen >= sizeof(struct sctp_paddrthlds)) {
                optlen = sizeof(struct sctp_paddrthlds);
        } else if (optlen >= ALIGN(offsetof(struct sctp_paddrthlds,
                                            spt_pathcpthld), 4))
                optlen = ALIGN(offsetof(struct sctp_paddrthlds,
                                        spt_pathcpthld), 4);
                val.spt_pathcpthld = 0xffff;
        else {
                return -EINVAL;
        }

        if (copy_from_user(&val, (struct sctp_paddrthlds __user *)optval,
                           optlen))
                return -EFAULT;

in sctp_getsockopt_paddr_thresholds():

        if (len >= sizeof(struct sctp_paddrthlds))
                len = sizeof(struct sctp_paddrthlds);
        else if (len >= ALIGN(offsetof(struct sctp_paddrthlds,
                                       spt_pathcpthld), 4))
                len = ALIGN(offsetof(struct sctp_paddrthlds,
                                     spt_pathcpthld), 4);
        else
                return -EINVAL;

        if (copy_from_user(&val, (struct sctp_paddrthlds __user *)optval, len))
                return -EFAULT;

So adding an extra field breaks existing application binaries
that use this option.

I've not checked the other patches or similar fubar.

        David

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