Merge tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Pull BPF fixes from Daniel Borkmann:

 - Fix BPF verifier to preserve full pointer state for commuted
   scalar += pointer arithmetic (Yiyang Chen, Eduard Zingerman)

 - Fix a use-after-free of request sockets in the BPF TCP iterator
   batching (Jose Fernandez)

 - Fix a use-after-free of sk_redir in the BPF sockmap send verdict
   path (Chengfeng Ye)

 - Fix a netns reference imbalance in the BPF conntrack kfuncs
   (Chengfeng Ye)

 - Fix bpf_get_fsverity_digest() dynptr assumptions and silent
   digest truncation (Eric Biggers)

 - Fix bpf_tcp_{gen,check}_syncookie to check sk_state before
   sk_protocol to make sure it is a full socket (Luxiao Xu)

 - Fix rqspinlock to reset the tail when preserving the queue
   on deadlock (Kumar Kartikeya Dwivedi)

* tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  rqspinlock: Reset tail when preserving queue on deadlock
  bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie
  fsverity: Fix silent truncation in bpf_get_fsverity_digest()
  fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions
  bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch()
  bpf: Fix netns reference imbalance in conntrack kfuncs
  bpf, sockmap: Fix sk_redir use-after-free in send verdict
  selftests/bpf: Cover commuted pointer state propagation
  bpf: Propagate untrusted pointer state in commuted arithmetic
  bpf: Preserve pointer state for commuted arithmetic
  bpf: Simplify sanitize_err() signature

fs/verity/measure.c

@@ -122,11 +122,11 @@ __bpf_kfunc int bpf_get_fsverity_digest(struct file *file, const struct bpf_dynp
 {
 	const struct bpf_dynptr_kern *digest_ptr = (struct bpf_dynptr_kern *)digest_p;
 	const struct inode *inode = file_inode(file);
-	u32 dynptr_sz = __bpf_dynptr_size(digest_ptr);
+	u64 dynptr_sz = __bpf_dynptr_size(digest_ptr);
 	struct fsverity_digest *arg;
 	const struct fsverity_info *vi;
 	const struct fsverity_hash_alg *hash_alg;
-	int out_digest_sz;
+	u64 out_digest_sz;
 
 	if (dynptr_sz < sizeof(struct fsverity_digest))
 		return -EINVAL;
@@ -144,17 +144,20 @@ __bpf_kfunc int bpf_get_fsverity_digest(struct file *file, const struct bpf_dynp
 
 	hash_alg = vi->tree_params.hash_alg;
 
+	out_digest_sz = dynptr_sz - sizeof(struct fsverity_digest);
+	if (out_digest_sz < hash_alg->digest_size)
+		return -EOVERFLOW;
+
 	arg->digest_algorithm = hash_alg - fsverity_hash_algs;
 	arg->digest_size = hash_alg->digest_size;
 
-	out_digest_sz = dynptr_sz - sizeof(struct fsverity_digest);
-
 	/* copy digest */
-	memcpy(arg->digest, vi->file_digest,  min_t(int, hash_alg->digest_size, out_digest_sz));
+	memcpy(arg->digest, vi->file_digest, hash_alg->digest_size);
 
 	/* fill the extra buffer with zeros */
 	if (out_digest_sz > hash_alg->digest_size)
-		memset(arg->digest + arg->digest_size, 0, out_digest_sz - hash_alg->digest_size);
+		memset(arg->digest + hash_alg->digest_size, 0,
+		       out_digest_sz - hash_alg->digest_size);
 
 	return 0;
 }

kernel/bpf/rqspinlock.c

@@ -572,9 +572,10 @@ int __lockfunc resilient_queued_spin_lock_slowpath(rqspinlock_t *lock, u32 val)
 
 	/* Disable queue destruction when we detect deadlocks. */
 	if (ret == -EDEADLK) {
-		if (!next)
+		if (!try_cmpxchg_tail(lock, tail, 0)) {
 			next = smp_cond_load_relaxed(&node->next, (VAL));
-		arch_mcs_spin_unlock_contended(&next->locked);
+			arch_mcs_spin_unlock_contended(&next->locked);
+		}
 		goto err_release_node;
 	}
 

kernel/bpf/verifier.c

@@ -13557,23 +13557,21 @@ static void sanitize_mark_insn_seen(struct bpf_verifier_env *env)
 		env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
 }
 
-static int sanitize_err(struct bpf_verifier_env *env,
-			const struct bpf_insn *insn, int reason,
-			const struct bpf_reg_state *off_reg,
-			const struct bpf_reg_state *dst_reg)
+static int sanitize_err(struct bpf_verifier_env *env, const struct bpf_insn *insn, int reason)
 {
 	static const char *err = "pointer arithmetic with it prohibited for !root";
 	const char *op = BPF_OP(insn->code) == BPF_ADD ? "add" : "sub";
 	u32 dst = insn->dst_reg, src = insn->src_reg;
+	struct bpf_reg_state *regs = cur_regs(env);
 
 	switch (reason) {
 	case REASON_BOUNDS:
 		verbose(env, "R%d has unknown scalar with mixed signed bounds, %s\n",
-			off_reg == dst_reg ? dst : src, err);
+			regs[src].type == SCALAR_VALUE ? src : dst, err);
 		break;
 	case REASON_TYPE:
 		verbose(env, "R%d has pointer with unsupported alu operation, %s\n",
-			off_reg == dst_reg ? src : dst, err);
+			regs[src].type == SCALAR_VALUE ? dst : src, err);
 		break;
 	case REASON_PATHS:
 		verbose(env, "R%d tried to %s from different maps, paths or scalars, %s\n",
@@ -13709,13 +13707,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	/*
-	 * Accesses to untrusted PTR_TO_MEM are done through probe
-	 * instructions, hence no need to track offsets.
-	 */
-	if (base_type(ptr_reg->type) == PTR_TO_MEM && (ptr_reg->type & PTR_UNTRUSTED))
-		return 0;
-
 	switch (base_type(ptr_reg->type)) {
 	case PTR_TO_CTX:
 	case PTR_TO_MAP_VALUE:
@@ -13745,11 +13736,19 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	/* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
-	 * The id may be overwritten later if we create a new variable offset.
+	/* For 'scalar += pointer', dst_reg inherits the complete pointer
+	 * register state. Individual fields may be adjusted later by pointer
+	 * arithmetic. Callers guarantee that below does not overwrite off_reg.
 	 */
-	dst_reg->type = ptr_reg->type;
-	dst_reg->id = ptr_reg->id;
+	if (dst_reg != ptr_reg)
+		*dst_reg = *ptr_reg;
+
+	/*
+	 * Accesses to untrusted PTR_TO_MEM are done through probe
+	 * instructions, hence no need to track offsets.
+	 */
+	if (base_type(ptr_reg->type) == PTR_TO_MEM && (ptr_reg->type & PTR_UNTRUSTED))
+		return 0;
 
 	if (!check_reg_sane_offset_scalar(env, off_reg, ptr_reg->type) ||
 	    !check_reg_sane_offset_ptr(env, ptr_reg, ptr_reg->type))
@@ -13762,7 +13761,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg,
 				       &info, false);
 		if (ret < 0)
-			return sanitize_err(env, insn, ret, off_reg, dst_reg);
+			return sanitize_err(env, insn, ret);
 	}
 
 	switch (opcode) {
@@ -13792,7 +13791,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		}
 		break;
 	case BPF_SUB:
-		if (dst_reg == off_reg) {
+		if (dst_reg != ptr_reg) {
 			/* scalar -= pointer.  Creates an unknown scalar */
 			verbose(env, "R%d tried to subtract pointer from scalar\n",
 				dst);
@@ -13855,7 +13854,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 			return -EFAULT;
 		}
 		if (ret < 0)
-			return sanitize_err(env, insn, ret, off_reg, dst_reg);
+			return sanitize_err(env, insn, ret);
 	}
 
 	return 0;
@@ -14607,7 +14606,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 	if (sanitize_needed(opcode)) {
 		ret = sanitize_val_alu(env, insn);
 		if (ret < 0)
-			return sanitize_err(env, insn, ret, NULL, NULL);
+			return sanitize_err(env, insn, ret);
 	}
 
 	/* Calculate sign/unsigned bounds and tnum for alu32 and alu64 bit ops.
@@ -14810,8 +14809,8 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				err = mark_chain_precision(env, insn->dst_reg);
 				if (err)
 					return err;
-				return adjust_ptr_min_max_vals(env, insn,
-							       src_reg, dst_reg);
+				off_reg = *dst_reg;
+				return adjust_ptr_min_max_vals(env, insn, src_reg, &off_reg);
 			}
 		} else if (ptr_reg) {
 			/* pointer += scalar */

net/core/filter.c

@@ -7684,7 +7684,7 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
 		return -EINVAL;
 
 	/* sk_listener() allows TCP_NEW_SYN_RECV, which makes no sense here. */
-	if (sk->sk_protocol != IPPROTO_TCP || sk->sk_state != TCP_LISTEN)
+	if (sk->sk_state != TCP_LISTEN || sk->sk_protocol != IPPROTO_TCP)
 		return -EINVAL;
 
 	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_syncookies))
@@ -7757,7 +7757,7 @@ BPF_CALL_5(bpf_tcp_gen_syncookie, struct sock *, sk, void *, iph, u32, iph_len,
 	if (unlikely(!sk || th_len < sizeof(*th) || th_len != th->doff * 4))
 		return -EINVAL;
 
-	if (sk->sk_protocol != IPPROTO_TCP || sk->sk_state != TCP_LISTEN)
+	if (sk->sk_state != TCP_LISTEN || sk->sk_protocol != IPPROTO_TCP)
 		return -EINVAL;
 
 	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_syncookies))

net/ipv4/tcp_bpf.c

@@ -469,6 +469,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 	case __SK_REDIRECT:
 		redir_ingress = psock->redir_ingress;
 		sk_redir = psock->sk_redir;
+		sock_hold(sk_redir);
 		sk_msg_apply_bytes(psock, tosend);
 		if (!psock->apply_bytes) {
 			/* Clean up before releasing the sock lock. */
@@ -489,6 +490,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 
 		if (eval == __SK_REDIRECT)
 			sock_put(sk_redir);
+		sock_put(sk_redir);
 
 		lock_sock(sk);
 		sk_mem_uncharge(sk, sent);

net/ipv4/tcp_ipv4.c

@@ -3078,24 +3078,24 @@ static unsigned int bpf_iter_tcp_established_batch(struct seq_file *seq,
 {
 	struct bpf_tcp_iter_state *iter = seq->private;
 	struct hlist_nulls_node *node;
-	unsigned int expected = 1;
-	struct sock *sk;
+	struct sock *sk = *start_sk;
+	unsigned int expected = 0;
 
-	sock_hold(*start_sk);
-	iter->batch[iter->end_sk++].sk = *start_sk;
-
-	sk = sk_nulls_next(*start_sk);
 	*start_sk = NULL;
 	sk_nulls_for_each_from(sk, node) {
-		if (seq_sk_match(seq, sk)) {
-			if (iter->end_sk < iter->max_sk) {
-				sock_hold(sk);
-				iter->batch[iter->end_sk++].sk = sk;
-			} else if (!*start_sk) {
-				/* Remember where we left off. */
-				*start_sk = sk;
-			}
-			expected++;
+		if (!seq_sk_match(seq, sk))
+			continue;
+		expected++;
+		if (iter->end_sk < iter->max_sk) {
+			/* reqsk_queue_hash_req() inserts with sk_refcnt == 0
+			 * and refcount_set()s it after the bucket lock drops.
+			 */
+			if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
+				continue;
+			iter->batch[iter->end_sk++].sk = sk;
+		} else if (!*start_sk) {
+			/* Remember where we left off. */
+			*start_sk = sk;
 		}
 	}
 
@@ -3133,12 +3133,13 @@ static struct sock *bpf_iter_tcp_batch(struct seq_file *seq)
 	struct sock *sk;
 	int err;
 
+again:
 	sk = bpf_iter_tcp_resume(seq);
 	if (!sk)
 		return NULL; /* Done */
 
 	expected = bpf_iter_fill_batch(seq, &sk);
-	if (likely(iter->end_sk == expected))
+	if (likely(!sk))
 		goto done;
 
 	/* Batch size was too small. */
@@ -3157,7 +3158,7 @@ static struct sock *bpf_iter_tcp_batch(struct seq_file *seq)
 		return NULL; /* Done */
 
 	expected = bpf_iter_fill_batch(seq, &sk);
-	if (likely(iter->end_sk == expected))
+	if (likely(!sk))
 		goto done;
 
 	/* Batch size was still too small. Hold onto the lock while we try
@@ -3170,10 +3171,14 @@ static struct sock *bpf_iter_tcp_batch(struct seq_file *seq)
 		return ERR_PTR(err);
 	}
 
-	expected = bpf_iter_fill_batch(seq, &sk);
-	WARN_ON_ONCE(iter->end_sk != expected);
+	bpf_iter_fill_batch(seq, &sk);
+	WARN_ON_ONCE(sk);
 done:
 	bpf_iter_tcp_unlock_bucket(seq);
+	if (unlikely(!iter->end_sk)) {
+		++iter->state.bucket;
+		goto again;
+	}
 	return iter->batch[0].sk;
 }
 

net/netfilter/nf_conntrack_bpf.c

@@ -122,42 +122,54 @@ __bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
 	struct nf_conntrack_tuple otuple, rtuple;
 	struct nf_conntrack_zone ct_zone;
 	struct nf_conn *ct;
+	u8 ct_zone_dir = 0;
+	u16 ct_zone_id;
+	s32 netns_id;
+	u8 l4proto;
 	int err;
 
 	if (!(opts_len == NF_BPF_CT_OPTS_SZ || opts_len == 12))
 		return ERR_PTR(-EINVAL);
+
+	netns_id = READ_ONCE(opts->netns_id);
+	l4proto = READ_ONCE(opts->l4proto);
+	ct_zone_id = READ_ONCE(opts->ct_zone_id);
 	if (opts_len == NF_BPF_CT_OPTS_SZ) {
-		if (opts->reserved[0] || opts->reserved[1] || opts->reserved[2])
+		ct_zone_dir = READ_ONCE(opts->ct_zone_dir);
+		if (READ_ONCE(opts->reserved[0]) ||
+		    READ_ONCE(opts->reserved[1]) ||
+		    READ_ONCE(opts->reserved[2]))
 			return ERR_PTR(-EINVAL);
 	} else {
-		if (opts->ct_zone_id)
+		if (ct_zone_id)
 			return ERR_PTR(-EINVAL);
 	}
 
-	if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
+	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
 		return ERR_PTR(-EINVAL);
 
-	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, l4proto,
 				    IP_CT_DIR_ORIGINAL, &otuple);
 	if (err < 0)
 		return ERR_PTR(err);
 
-	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, l4proto,
 				    IP_CT_DIR_REPLY, &rtuple);
 	if (err < 0)
 		return ERR_PTR(err);
 
-	if (opts->netns_id >= 0) {
-		net = get_net_ns_by_id(net, opts->netns_id);
+	if (netns_id >= 0) {
+		net = get_net_ns_by_id(net, netns_id);
 		if (unlikely(!net))
 			return ERR_PTR(-ENONET);
 	}
 
 	if (opts_len == NF_BPF_CT_OPTS_SZ) {
-		if (opts->ct_zone_dir == 0)
-			opts->ct_zone_dir = NF_CT_DEFAULT_ZONE_DIR;
-		nf_ct_zone_init(&ct_zone,
-				opts->ct_zone_id, opts->ct_zone_dir, 0);
+		if (ct_zone_dir == 0) {
+			ct_zone_dir = NF_CT_DEFAULT_ZONE_DIR;
+			opts->ct_zone_dir = ct_zone_dir;
+		}
+		nf_ct_zone_init(&ct_zone, ct_zone_id, ct_zone_dir, 0);
 	} else {
 		ct_zone = nf_ct_zone_dflt;
 	}
@@ -171,7 +183,7 @@ __bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
 	__nf_ct_set_timeout(ct, timeout * HZ);
 
 out:
-	if (opts->netns_id >= 0)
+	if (netns_id >= 0)
 		put_net(net);
 
 	return ct;
@@ -186,46 +198,58 @@ static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
 	struct nf_conntrack_tuple tuple;
 	struct nf_conntrack_zone ct_zone;
 	struct nf_conn *ct;
+	u8 ct_zone_dir = 0;
+	u16 ct_zone_id;
+	s32 netns_id;
+	u8 l4proto;
 	int err;
 
 	if (!opts || !bpf_tuple)
 		return ERR_PTR(-EINVAL);
 	if (!(opts_len == NF_BPF_CT_OPTS_SZ || opts_len == 12))
 		return ERR_PTR(-EINVAL);
+
+	netns_id = READ_ONCE(opts->netns_id);
+	l4proto = READ_ONCE(opts->l4proto);
+	ct_zone_id = READ_ONCE(opts->ct_zone_id);
 	if (opts_len == NF_BPF_CT_OPTS_SZ) {
-		if (opts->reserved[0] || opts->reserved[1] || opts->reserved[2])
+		ct_zone_dir = READ_ONCE(opts->ct_zone_dir);
+		if (READ_ONCE(opts->reserved[0]) ||
+		    READ_ONCE(opts->reserved[1]) ||
+		    READ_ONCE(opts->reserved[2]))
 			return ERR_PTR(-EINVAL);
 	} else {
-		if (opts->ct_zone_id)
+		if (ct_zone_id)
 			return ERR_PTR(-EINVAL);
 	}
-	if (unlikely(opts->l4proto != IPPROTO_TCP && opts->l4proto != IPPROTO_UDP))
+	if (unlikely(l4proto != IPPROTO_TCP && l4proto != IPPROTO_UDP))
 		return ERR_PTR(-EPROTO);
-	if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
+	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
 		return ERR_PTR(-EINVAL);
 
-	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, l4proto,
 				    IP_CT_DIR_ORIGINAL, &tuple);
 	if (err < 0)
 		return ERR_PTR(err);
 
-	if (opts->netns_id >= 0) {
-		net = get_net_ns_by_id(net, opts->netns_id);
+	if (netns_id >= 0) {
+		net = get_net_ns_by_id(net, netns_id);
 		if (unlikely(!net))
 			return ERR_PTR(-ENONET);
 	}
 
 	if (opts_len == NF_BPF_CT_OPTS_SZ) {
-		if (opts->ct_zone_dir == 0)
-			opts->ct_zone_dir = NF_CT_DEFAULT_ZONE_DIR;
-		nf_ct_zone_init(&ct_zone,
-				opts->ct_zone_id, opts->ct_zone_dir, 0);
+		if (ct_zone_dir == 0) {
+			ct_zone_dir = NF_CT_DEFAULT_ZONE_DIR;
+			opts->ct_zone_dir = ct_zone_dir;
+		}
+		nf_ct_zone_init(&ct_zone, ct_zone_id, ct_zone_dir, 0);
 	} else {
 		ct_zone = nf_ct_zone_dflt;
 	}
 
 	hash = nf_conntrack_find_get(net, &ct_zone, &tuple);
-	if (opts->netns_id >= 0)
+	if (netns_id >= 0)
 		put_net(net);
 	if (!hash)
 		return ERR_PTR(-ENOENT);

tools/testing/selftests/bpf/progs/dynptr_fail.c

@@ -1635,6 +1635,36 @@ static int callback(__u32 index, void *data)
         return 0;
 }
 
+/* A commuted add should preserve the parent id of a dynptr data slice. */
+SEC("?raw_tp")
+__failure __msg("invalid mem access 'scalar'")
+int dynptr_slice_commuted_invalidate(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	__u32 *slice, *derived;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(__u32), 0, &ptr);
+
+	slice = bpf_dynptr_data(&ptr, 0, sizeof(__u32));
+	if (!slice)
+		goto done;
+
+	asm volatile ("%[dst] = 0;"
+		"%[dst] += %[src];"
+		"%[src] = 0;"
+		: [dst]"=&r"(derived), [src]"+r"(slice)
+		:
+		: "memory");
+
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	val = *derived;
+	return 0;
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
 /* If the dynptr is written into in a callback function, its data
  * slices should be invalidated as well.
  */

tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c

@@ -226,4 +226,21 @@ int null_check(void *ctx)
 	return 0;
 }
 
+SEC("socket")
+__success
+__retval(1)
+int ldx_is_ok_commuted_addr(void *ctx)
+{
+	int v, *p, *derived;
+
+	v = 1;
+	p = bpf_rdonly_cast(&v, 0);
+	asm volatile ("%[dst] = 0;"
+		"%[dst] += %[src];"
+		: [dst]"=&r"(derived)
+		: [src]"r"(p)
+		: "memory");
+	return *derived;
+}
+
 char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/verifier_basic_stack.c

@@ -97,4 +97,45 @@ __naked void misaligned_read_from_stack(void)
 "	::: __clobber_all);
 }
 
+SEC("socket")
+__description("stack pointer arithmetic preserves frame number")
+__failure __msg("R7 invalid mem access 'scalar'")
+__naked void stack_ptr_arith_preserves_frameno(void)
+{
+	asm volatile ("\
+		r3 = 0;						\
+		*(u64 *)(r10 - 8) = r3;			\
+		r1 = %[map_hash_8b] ll;			\
+		r2 = r10;					\
+		r2 += -8;					\
+		call %[bpf_map_lookup_elem];		\
+		if r0 != 0 goto +2;			\
+		r0 = 0;						\
+		exit;						\
+		r1 = r0;					\
+		r2 = 0;						\
+		r3 = 0;						\
+		call stack_ptr_arith_preserves_frameno_subprog;\
+		r0 = 0;						\
+		exit;						\
+	":
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_hash_8b)
+	: __clobber_all);
+}
+
+static __used __naked void stack_ptr_arith_preserves_frameno_subprog(void)
+{
+	asm volatile ("\
+		*(u64 *)(r10 - 8) = r1;			\
+		r6 = -8;					\
+		r6 += r10;					\
+		*(u64 *)(r6 + 0) = r2;			\
+		r7 = *(u64 *)(r10 - 8);			\
+		*(u64 *)(r7 + 0) = r3;			\
+		r0 = 0;						\
+		exit;						\
+	"::: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";