nfp: bpf: double check vNIC capabilities after object sharing

Program translation stage checks that program can be offloaded to
the netdev which was passed during the load (bpf_attr->prog_ifindex).
After program sharing was introduced, however, the netdev on which
program is loaded can theoretically be different, and therefore
we should recheck the program size and max stack size at load time.

This was found by code inspection, AFAIK today all vNICs have
identical caps.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

drivers/net/ethernet/netronome/nfp/bpf/main.h

@@ -441,6 +441,7 @@ struct nfp_bpf_subprog_info {
  * @prog: machine code
  * @prog_len: number of valid instructions in @prog array
  * @__prog_alloc_len: alloc size of @prog array
+ * @stack_size: total amount of stack used
  * @verifier_meta: temporary storage for verifier's insn meta
  * @type: BPF program type
  * @last_bpf_off: address of the last instruction translated from BPF
@@ -465,6 +466,8 @@ struct nfp_prog {
 	unsigned int prog_len;
 	unsigned int __prog_alloc_len;
 
+	unsigned int stack_size;
+
 	struct nfp_insn_meta *verifier_meta;
 
 	enum bpf_prog_type type;

drivers/net/ethernet/netronome/nfp/bpf/offload.c

@@ -489,7 +489,7 @@ nfp_net_bpf_load(struct nfp_net *nn, struct bpf_prog *prog,
 		 struct netlink_ext_ack *extack)
 {
 	struct nfp_prog *nfp_prog = prog->aux->offload->dev_priv;
-	unsigned int max_mtu;
+	unsigned int max_mtu, max_stack, max_prog_len;
 	dma_addr_t dma_addr;
 	void *img;
 	int err;
@@ -500,6 +500,18 @@ nfp_net_bpf_load(struct nfp_net *nn, struct bpf_prog *prog,
 		return -EOPNOTSUPP;
 	}
 
+	max_stack = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
+	if (nfp_prog->stack_size > max_stack) {
+		NL_SET_ERR_MSG_MOD(extack, "stack too large");
+		return -EOPNOTSUPP;
+	}
+
+	max_prog_len = nn_readw(nn, NFP_NET_CFG_BPF_MAX_LEN);
+	if (nfp_prog->prog_len > max_prog_len) {
+		NL_SET_ERR_MSG_MOD(extack, "program too long");
+		return -EOPNOTSUPP;
+	}
+
 	img = nfp_bpf_relo_for_vnic(nfp_prog, nn->app_priv);
 	if (IS_ERR(img))
 		return PTR_ERR(img);

drivers/net/ethernet/netronome/nfp/bpf/verifier.c

@@ -747,9 +747,9 @@ nfp_bpf_get_stack_usage(struct nfp_prog *nfp_prog, unsigned int cnt)
 
 static int nfp_bpf_finalize(struct bpf_verifier_env *env)
 {
-	unsigned int stack_size, stack_needed;
 	struct bpf_subprog_info *info;
 	struct nfp_prog *nfp_prog;
+	unsigned int max_stack;
 	struct nfp_net *nn;
 	int i;
 
@@ -777,11 +777,12 @@ static int nfp_bpf_finalize(struct bpf_verifier_env *env)
 	}
 
 	nn = netdev_priv(env->prog->aux->offload->netdev);
-	stack_size = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
-	stack_needed = nfp_bpf_get_stack_usage(nfp_prog, env->prog->len);
-	if (stack_needed > stack_size) {
+	max_stack = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
+	nfp_prog->stack_size = nfp_bpf_get_stack_usage(nfp_prog,
+						       env->prog->len);
+	if (nfp_prog->stack_size > max_stack) {
 		pr_vlog(env, "stack too large: program %dB > FW stack %dB\n",
-			stack_needed, stack_size);
+			nfp_prog->stack_size, max_stack);
 		return -EOPNOTSUPP;
 	}