test_select_reuseport fails on s390 due to verifier rejecting
test_select_reuseport_kern.o with the following message:
; data_check.eth_protocol = reuse_md->eth_protocol;
18: (69) r1 = *(u16 *)(r6 +22)
invalid bpf_context access off=22 size=2
This is because on big-endian machines casts from __u32 to __u16 are
generated by referencing the respective variable as __u16 with an offset
of 2 (as opposed to 0 on little-endian machines).
The verifier already has all the infrastructure in place to allow such
accesses, it's just that they are not explicitly enabled for
eth_protocol field. Enable them for eth_protocol field by using
bpf_ctx_range instead of offsetof.
Ditto for ip_protocol, bind_inany and len, since they already allow
narrowing, and the same problem can arise when working with them.
Fixes: 2dbb9b9e6df6 ("bpf: Introduce BPF_PROG_TYPE_SK_REUSEPORT")
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
---
net/core/filter.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 7878f918b8c0..4c6a252d4212 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8757,13 +8757,13 @@ sk_reuseport_is_valid_access(int off, int size,
return size == size_default;
/* Fields that allow narrowing */
- case offsetof(struct sk_reuseport_md, eth_protocol):
+ case bpf_ctx_range(struct sk_reuseport_md, eth_protocol):
if (size < FIELD_SIZEOF(struct sk_buff, protocol))
return false;
/* fall through */
- case offsetof(struct sk_reuseport_md, ip_protocol):
- case offsetof(struct sk_reuseport_md, bind_inany):
- case offsetof(struct sk_reuseport_md, len):
+ case bpf_ctx_range(struct sk_reuseport_md, ip_protocol):
+ case bpf_ctx_range(struct sk_reuseport_md, bind_inany):
+ case bpf_ctx_range(struct sk_reuseport_md, len):
bpf_ctx_record_field_size(info, size_default);
return bpf_ctx_narrow_access_ok(off, size, size_default);
--
2.21.0
