From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Tue, 8 May 2018 19:37:06 -0700
Subject: bpf: xdp: allow offloads to store into rx_queue_index
Patch-mainline: v4.18-rc1
Git-commit: 0d8300325660f81787892a1c58dc1f9428a67143
References: bsc#1109837

It's fairly easy for offloaded XDP programs to select the RX queue
packets go to.  We need a way of expressing this in the software.
Allow write to the rx_queue_index field of struct xdp_md for
device-bound programs.

Skip convert_ctx_access callback entirely for offloads.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/bpf.h   |    2 +-
 kernel/bpf/verifier.c |    2 +-
 net/core/filter.c     |    9 ++++++++-
 3 files changed, 10 insertions(+), 3 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -598,7 +598,7 @@ bool bpf_offload_dev_match(struct bpf_pr
 #if defined(CONFIG_NET) && defined(CONFIG_BPF_SYSCALL)
 int bpf_prog_offload_init(struct bpf_prog *prog, union bpf_attr *attr);
 
-static inline bool bpf_prog_is_dev_bound(struct bpf_prog_aux *aux)
+static inline bool bpf_prog_is_dev_bound(const struct bpf_prog_aux *aux)
 {
 	return aux->offload_requested;
 }
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5227,7 +5227,7 @@ static int convert_ctx_accesses(struct b
 		}
 	}
 
-	if (!ops->convert_ctx_access)
+	if (!ops->convert_ctx_access || bpf_prog_is_dev_bound(env->prog->aux))
 		return 0;
 
 	insn = env->prog->insnsi + delta;
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4519,8 +4519,15 @@ static bool xdp_is_valid_access(int off,
 				const struct bpf_prog *prog,
 				struct bpf_insn_access_aux *info)
 {
-	if (type == BPF_WRITE)
+	if (type == BPF_WRITE) {
+		if (bpf_prog_is_dev_bound(prog->aux)) {
+			switch (off) {
+			case offsetof(struct xdp_md, rx_queue_index):
+				return __is_valid_xdp_access(off, size);
+			}
+		}
 		return false;
+	}
 
 	switch (off) {
 	case offsetof(struct xdp_md, data):