Merge branch 'fix-gso_segs'

Eric Dumazet says:

====================
First patch changes the kernel, second patch
adds a new test.

Note that other patches might be needed to take
care of similar issues in sock_ops_convert_ctx_access()
and SOCK_OPS_GET_FIELD()
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

net/core/filter.c

@@ -7455,12 +7455,12 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 	case offsetof(struct __sk_buff, gso_segs):
 		/* si->dst_reg = skb_shinfo(SKB); */
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
-				      si->dst_reg, si->src_reg,
-				      offsetof(struct sk_buff, head));
 		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
 				      BPF_REG_AX, si->src_reg,
 				      offsetof(struct sk_buff, end));
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
+				      si->dst_reg, si->src_reg,
+				      offsetof(struct sk_buff, head));
 		*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);
 #else
 		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),

tools/testing/selftests/bpf/verifier/ctx_skb.c

@@ -974,6 +974,17 @@
 	.result = ACCEPT,
 	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
 },
+{
+	"read gso_segs from CGROUP_SKB",
+	.insns = {
+	BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+		    offsetof(struct __sk_buff, gso_segs)),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+},
 {
 	"write gso_segs from CGROUP_SKB",
 	.insns = {