tcp: Specify cmsgbuf is user pointer for receive zerocopy.

A prior change (4126eac58915) introduces separate handling for
->msg_control depending on whether the pointer is a kernel or user
pointer. However, while tcp receive zerocopy is using this field, it
is not properly annotating that the buffer in this case is a user
pointer. This can cause faults when the improper mechanism is used
within put_cmsg().

This patch simply annotates tcp receive zerocopy's use as explicitly
being a user pointer.

Fixes: 123d42faa54f ("tcp: Add receive timestamp support for receive zerocopy.")
Signed-off-by: Arjun Roy <arjunroy@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210506223530.2266456-1-arjunroy.kdev@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e14fd0c50c10222b4b6b078b21e0b076343febff..f1c1f9e3de723fc8716e1c9c25ff25de72ae00a6 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2039,6 +2039,7 @@ static void tcp_zc_finalize_rx_tstamp(struct sock *sk,
                (__kernel_size_t)zc->msg_controllen;
        cmsg_dummy.msg_flags = in_compat_syscall()
                ? MSG_CMSG_COMPAT : 0;
+       cmsg_dummy.msg_control_is_user = true;
        zc->msg_flags = 0;
        if (zc->msg_control == msg_control_addr &&
            zc->msg_controllen == cmsg_dummy.msg_controllen) {