Running the following sequence is currently broken:
# tc qdisc add dev foo clsact
# tc filter replace dev foo ingress prio 1 handle 1 bpf da obj bar.o
# tc filter replace dev foo ingress prio 1 handle 1 bpf da obj bar.o
RTNETLINK answers: Invalid argument
The normal expectation on kernel side is that the second command
succeeds replacing the existing program. However, what happens is
in cls_bpf_change(), we bail out with err in the second run in
cls_bpf_offload(). The EINVAL comes directly in cls_bpf_offload()
when comparing prog vs oldprog's gen_flags. In case of above
replace the new prog's gen_flags are 0, but the old ones are 8,
which means TCA_CLS_FLAGS_NOT_IN_HW is set (e.g. drivers not having
cls_bpf offload).
Fix 102740bd9436 ("cls_bpf: fix offload assumptions after callback
conversion") in the following way: gen_flags from user space passed
down via netlink cannot include status flags like TCA_CLS_FLAGS_IN_HW
or TCA_CLS_FLAGS_NOT_IN_HW as opposed to oldprog that we previously
loaded. Therefore, it doesn't make any sense to include them in the
gen_flags comparison with the new prog before we even attempt to
offload. Thus, lets fix this before 4.15 goes out.
Fixes: 102740bd9436 ("cls_bpf: fix offload assumptions after callback
conversion")
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
net/sched/cls_bpf.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 8d78e7f..a62586e 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -183,10 +183,17 @@ static int cls_bpf_offload_cmd(struct tcf_proto *tp,
struct cls_bpf_prog *prog,
return 0;
}
+static u32 cls_bpf_flags(u32 flags)
+{
+ return flags & CLS_BPF_SUPPORTED_GEN_FLAGS;
+}
+
static int cls_bpf_offload(struct tcf_proto *tp, struct cls_bpf_prog *prog,
struct cls_bpf_prog *oldprog)
{
- if (prog && oldprog && prog->gen_flags != oldprog->gen_flags)
+ if (prog && oldprog &&
+ cls_bpf_flags(prog->gen_flags) !=
+ cls_bpf_flags(oldprog->gen_flags))
return -EINVAL;
if (prog && tc_skip_hw(prog->gen_flags))
--
2.9.5
