From: Ilya Leoshkevich iii@linux.ibm.com
[ Upstream commit 2c238177bd7f4b14bdf7447cc1cd9bb791f147e6 ]
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@linux.ibm.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 534c310bb0893..7aee6f368754a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8553,13 +8553,13 @@ 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);