Re: [net] tcp: Explicitly mark reserved field in tcp_zerocopy_receive args.

On Fri, Feb 5, 2021 at 10:57 PM David Ahern [off-list ref] wrote:

On 2/5/21 4:01 PM, Arjun Roy wrote:

quoted

From: Arjun Roy <redacted>

Explicitly define reserved field and require it to be 0-valued.

Fixes: 7eeba1706eba ("tcp: Add receive timestamp support for receive zerocopy.")
Signed-off-by: Arjun Roy <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <redacted>
Suggested-by: David Ahern <redacted>
Suggested-by: Leon Romanovsky <leon@kernel.org>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
---
 include/uapi/linux/tcp.h | 2 +-
 net/ipv4/tcp.c           | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 42fc5a640df4..8fc09e8638b3 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h

@@ -357,6 +357,6 @@ struct tcp_zerocopy_receive {
      __u64 msg_control; /* ancillary data */
      __u64 msg_controllen;
      __u32 msg_flags;
-     /* __u32 hole;  Next we must add >1 u32 otherwise length checks fail. */
+     __u32 reserved; /* set to 0 for now */
 };
 #endif /* _UAPI_LINUX_TCP_H */

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e1a17c6b473c..97aee57ab9b4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c

@@ -4159,6 +4159,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
              }
              if (copy_from_user(&zc, optval, len))
                      return -EFAULT;
+             if (zc.reserved)
+                     return -EOPNOTSUPP;

usually invalid values for uapi return -EINVAL

I'll send out a v2 with that changed then.

-Arjun