[PATCH net 2/2] bpf: fix two missing target_size settings in bpf_convert_ctx_access

[Daniel Borkmann]

When CONFIG_NET_SCHED or CONFIG_NET_RX_BUSY_POLL is /not/ set and
we try a narrow __sk_buff load of tc_index or napi_id, respectively,
then verifier rightfully complains that it's misconfigured, because
we need to set target_size in each of the two cases. The rewrite
for the ctx access is just a dummy op, but needs to pass, so fix
this up.

Fixes: f96da09473b5 ("bpf: simplify narrower ctx access")
Reported-by: Shubham Bansal <illusionist....@gmail.com>
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
---
 net/core/filter.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index f44fc22..6280a60 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3505,6 +3505,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type 
type,
                                              bpf_target_off(struct sk_buff, 
tc_index, 2,
                                                             target_size));
 #else
+               *target_size = 2;
                if (type == BPF_WRITE)
                        *insn++ = BPF_MOV64_REG(si->dst_reg, si->dst_reg);
                else
@@ -3520,6 +3521,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type 
type,
                *insn++ = BPF_JMP_IMM(BPF_JGE, si->dst_reg, MIN_NAPI_ID, 1);
                *insn++ = BPF_MOV64_IMM(si->dst_reg, 0);
 #else
+               *target_size = 4;
                *insn++ = BPF_MOV64_IMM(si->dst_reg, 0);
 #endif
                break;
-- 
1.9.3