Subject: [PATCH v3 bpf-next 1/9] bpf: introduce bpf_spin_lock

From: Alexei Starovoitov <[email-masked]>
Date: Tue, 22 Jan 2019 22:06:30 -0800

Introduce 'struct bpf_spin_lock' and bpf_spin_lock/unlock() helpers to let
bpf program serialize access to other variables.

Example:
struct hash_elem {
    int cnt;
    struct bpf_spin_lock lock;
};
struct hash_elem * val = bpf_map_lookup_elem(&hash_map, &key);
if (val) {
    bpf_spin_lock(&val->lock);
    val->cnt++;
    bpf_spin_unlock(&val->lock);
}

Restrictions and safety checks:
- bpf_spin_lock is only allowed inside HASH and ARRAY maps.
- BTF description of the map is mandatory for safety analysis.
- bpf program can take one bpf_spin_lock at a time, since two or more can
  cause dead locks.
- only one 'struct bpf_spin_lock' is allowed per map element.
  It drastically simplifies implementation yet allows bpf program to use
  any number of bpf_spin_locks.
- when bpf_spin_lock is taken the calls (either bpf2bpf or helpers) are not allowed.
- bpf program must bpf_spin_unlock() before return.
- bpf program can access 'struct bpf_spin_lock' only via
  bpf_spin_lock()/bpf_spin_unlock() helpers.
- load/store into 'struct bpf_spin_lock lock;' field is not allowed.
- to use bpf_spin_lock() helper the BTF description of map value must be
  a struct and have 'struct bpf_spin_lock anyname;' field at the top level.
  Nested lock inside another struct is not allowed.
- syscall map_lookup doesn't copy bpf_spin_lock field to user space.
- syscall map_update and program map_update do not update bpf_spin_lock field.
- bpf_spin_lock cannot be on the stack or inside networking packet.
  bpf_spin_lock can only be inside HASH or ARRAY map value.
- bpf_spin_lock is available to root only and to all program types.
- bpf_spin_lock is not allowed in inner maps of map-in-map.
- ld_abs is not allowed inside spin_lock-ed region.

Implementation details:
- on !SMP bpf_spin_lock() becomes nop
- on architectures that don't support queued_spin_lock trivial lock is used.
  Note that arch_spin_lock cannot be used, since not all archs agree that
  zero == unlocked and sizeof(arch_spinlock_t) != sizeof(__u32).
- presence of bpf_spin_lock inside map value could have been indicated via
  extra flag during map_create, but specifying it via BTF is cleaner.
  It provides introspection for map key/value and reduces user coding mistakes.

Next steps:
- allow bpf_spin_lock in other map types (like cgroup local storage)
- introduce BPF_F_LOCK flag for bpf_map_update() syscall and helper
  to request kernel to grab bpf_spin_lock before rewriting the value.
  That will serialize access to map elements.

Signed-off-by: Alexei Starovoitov <[email-masked]>
---
 include/linux/bpf.h          |  37 ++++++++-
 include/linux/bpf_verifier.h |   1 +
 include/linux/btf.h          |   1 +
 include/uapi/linux/bpf.h     |   7 +-
 kernel/bpf/arraymap.c        |   7 +-
 kernel/bpf/btf.c             |  42 ++++++++++
 kernel/bpf/core.c            |   2 +
 kernel/bpf/hashtab.c         |   6 +-
 kernel/bpf/helpers.c         |  57 ++++++++++++++
 kernel/bpf/map_in_map.c      |   5 ++
 kernel/bpf/syscall.c         |  21 ++++-
 kernel/bpf/verifier.c        | 149 ++++++++++++++++++++++++++++++++++-
 net/core/filter.c            |  16 +++-
 13 files changed, 335 insertions(+), 16 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e734f163bd0b..5ffa32ea7673 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -72,14 +72,15 @@ struct bpf_map {
 	u32 value_size;
 	u32 max_entries;
 	u32 map_flags;
-	u32 pages;
+	int spin_lock_off; /* >=0 valid offset, <0 error */
 	u32 id;
 	int numa_node;
 	u32 btf_key_type_id;
 	u32 btf_value_type_id;
 	struct btf *btf;
+	u32 pages;
 	bool unpriv_array;
-	/* 55 bytes hole */
+	/* 51 bytes hole */
 
 	/* The 3rd and 4th cacheline with misc members to avoid false sharing
 	 * particularly with refcounting.
@@ -91,6 +92,34 @@ struct bpf_map {
 	char name[BPF_OBJ_NAME_LEN];
 };
 
+static inline bool map_value_has_spin_lock(const struct bpf_map *map)
+{
+	return map->spin_lock_off >= 0;
+}
+
+static inline void check_and_init_map_lock(struct bpf_map *map, void *dst)
+{
+	if (likely(!map_value_has_spin_lock(map)))
+		return;
+	*(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
+		(struct bpf_spin_lock){};
+}
+
+/* copy everything but bpf_spin_lock */
+static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
+{
+	if (unlikely(map_value_has_spin_lock(map))) {
+		u32 off = map->spin_lock_off;
+
+		memcpy(dst, src, off);
+		memcpy(dst + off + sizeof(struct bpf_spin_lock),
+		       src + off + sizeof(struct bpf_spin_lock),
+		       map->value_size - off - sizeof(struct bpf_spin_lock));
+	} else {
+		memcpy(dst, src, map->value_size);
+	}
+}
+
 struct bpf_offload_dev;
 struct bpf_offloaded_map;
 
@@ -162,6 +191,7 @@ enum bpf_arg_type {
 	ARG_PTR_TO_CTX,		/* pointer to context */
 	ARG_ANYTHING,		/* any (initialized) argument is ok */
 	ARG_PTR_TO_SOCKET,	/* pointer to bpf_sock */
+	ARG_PTR_TO_SPIN_LOCK,	/* pointer to bpf_spin_lock */
 };
 
 /* type of values returned from helper functions */
@@ -869,7 +899,8 @@ extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
 extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
 extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
 extern const struct bpf_func_proto bpf_sk_redirect_map_proto;
-
+extern const struct bpf_func_proto bpf_spin_lock_proto;
+extern const struct bpf_func_proto bpf_spin_unlock_proto;
 extern const struct bpf_func_proto bpf_get_local_storage_proto;
 
 /* Shared helpers among cBPF and eBPF. */
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 573cca00a0e6..ff2ff2d9e810 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -148,6 +148,7 @@ struct bpf_verifier_state {
 	/* call stack tracking */
 	struct bpf_func_state *frame[MAX_CALL_FRAMES];
 	u32 curframe;
+	u32 active_spin_lock;
 	bool speculative;
 };
 
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 12502e25e767..455d31b55828 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -50,6 +50,7 @@ u32 btf_id(const struct btf *btf);
 bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   const struct btf_member *m,
 			   u32 expected_offset, u32 expected_size);
+int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 
 #ifdef CONFIG_BPF_SYSCALL
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 91c43884f295..30f9dfd40f13 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2421,7 +2421,9 @@ union bpf_attr {
 	FN(map_peek_elem),		\
 	FN(msg_push_data),		\
 	FN(msg_pop_data),		\
-	FN(rc_pointer_rel),
+	FN(rc_pointer_rel),		\
+	FN(spin_lock),			\
+	FN(spin_unlock),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3054,4 +3056,7 @@ struct bpf_line_info {
 	__u32	line_col;
 };
 
+struct bpf_spin_lock {
+	__u32	val;
+};
 #endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 25632a75d630..d6d979910a2a 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -270,9 +270,10 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 		memcpy(this_cpu_ptr(array->pptrs[index & array->index_mask]),
 		       value, map->value_size);
 	else
-		memcpy(array->value +
-		       array->elem_size * (index & array->index_mask),
-		       value, map->value_size);
+		copy_map_value(map,
+			       array->value +
+			       array->elem_size * (index & array->index_mask),
+			       value);
 	return 0;
 }
 
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 022ef9ca1296..03b1a7a6195c 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -355,6 +355,11 @@ static bool btf_type_is_struct(const struct btf_type *t)
 	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
 }
 
+static bool __btf_type_is_struct(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
+}
+
 static bool btf_type_is_array(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
@@ -2045,6 +2050,43 @@ static void btf_struct_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
 }
 
+/* find 'struct bpf_spin_lock' in map value.
+ * return >= 0 offset if found
+ * and < 0 in case of error
+ */
+int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
+{
+	const struct btf_member *member;
+	u32 i, off = -ENOENT;
+
+	if (!__btf_type_is_struct(t))
+		return -EINVAL;
+
+	for_each_member(i, t, member) {
+		const struct btf_type *member_type = btf_type_by_id(btf,
+								    member->type);
+		if (!__btf_type_is_struct(member_type))
+			continue;
+		if (member_type->size != sizeof(struct bpf_spin_lock))
+			continue;
+		if (strcmp(__btf_name_by_offset(btf, member_type->name_off),
+			   "bpf_spin_lock"))
+			continue;
+		if (off != -ENOENT)
+			/* only one 'struct bpf_spin_lock' is allowed */
+			return -E2BIG;
+		off = btf_member_bit_offset(t, member);
+		if (off % 8)
+			/* valid C code cannot generate such BTF */
+			return -EINVAL;
+		off /= 8;
+		if (off % __alignof__(struct bpf_spin_lock))
+			/* valid struct bpf_spin_lock will be 4 byte aligned */
+			return -EINVAL;
+	}
+	return off;
+}
+
 static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
 				u32 type_id, void *data, u8 bits_offset,
 				struct seq_file *m)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f908b9356025..497d0c4c123c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2036,6 +2036,8 @@ const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
 const struct bpf_func_proto bpf_map_push_elem_proto __weak;
 const struct bpf_func_proto bpf_map_pop_elem_proto __weak;
 const struct bpf_func_proto bpf_map_peek_elem_proto __weak;
+const struct bpf_func_proto bpf_spin_lock_proto __weak;
+const struct bpf_func_proto bpf_spin_unlock_proto __weak;
 
 const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
 const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 4b7c76765d9d..48a41bf65e1b 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -770,6 +770,8 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 			l_new = ERR_PTR(-ENOMEM);
 			goto dec_count;
 		}
+		check_and_init_map_lock(&htab->map,
+					l_new->key + round_up(key_size, 8));
 	}
 
 	memcpy(l_new->key, key, key_size);
@@ -792,7 +794,9 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 		if (!prealloc)
 			htab_elem_set_ptr(l_new, key_size, pptr);
 	} else {
-		memcpy(l_new->key + round_up(key_size, 8), value, size);
+		copy_map_value(&htab->map,
+			       l_new->key + round_up(key_size, 8),
+			       value);
 	}
 
 	l_new->hash = hash;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a74972b07e74..2e98e4caf5aa 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -221,6 +221,63 @@ const struct bpf_func_proto bpf_get_current_comm_proto = {
 	.arg2_type	= ARG_CONST_SIZE,
 };
 
+#ifndef CONFIG_QUEUED_SPINLOCKS
+struct dumb_spin_lock {
+	atomic_t val;
+};
+#endif
+
+notrace BPF_CALL_1(bpf_spin_lock, struct bpf_spin_lock *, lock)
+{
+#if defined(CONFIG_SMP)
+#ifdef CONFIG_QUEUED_SPINLOCKS
+	struct qspinlock *qlock = (void *)lock;
+
+	BUILD_BUG_ON(sizeof(*qlock) != sizeof(*lock));
+	queued_spin_lock(qlock);
+#else
+	struct dumb_spin_lock *qlock = (void *)lock;
+
+	BUILD_BUG_ON(sizeof(*qlock) != sizeof(*lock));
+	do {
+		while (atomic_read(&qlock->val) != 0)
+			cpu_relax();
+	} while (atomic_cmpxchg(&qlock->val, 0, 1) != 0);
+#endif
+#endif
+	return 0;
+}
+
+const struct bpf_func_proto bpf_spin_lock_proto = {
+	.func		= bpf_spin_lock,
+	.gpl_only	= false,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+};
+
+notrace BPF_CALL_1(bpf_spin_unlock, struct bpf_spin_lock *, lock)
+{
+#if defined(CONFIG_SMP)
+#ifdef CONFIG_QUEUED_SPINLOCKS
+	struct qspinlock *qlock = (void *)lock;
+
+	queued_spin_unlock(qlock);
+#else
+	struct dumb_spin_lock *qlock = (void *)lock;
+
+	atomic_set(&qlock->val, 0);
+#endif
+#endif
+	return 0;
+}
+
+const struct bpf_func_proto bpf_spin_unlock_proto = {
+	.func		= bpf_spin_unlock,
+	.gpl_only	= false,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+};
+
 #ifdef CONFIG_CGROUPS
 BPF_CALL_0(bpf_get_current_cgroup_id)
 {
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 99d243e1ad6e..920eff1b677b 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -36,6 +36,11 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		return ERR_PTR(-EINVAL);
 	}
 
+	if (map_value_has_spin_lock(inner_map)) {
+		fdput(f);
+		return ERR_PTR(-ENOTSUPP);
+	}
+
 	inner_map_meta = kzalloc(sizeof(*inner_map_meta), GFP_USER);
 	if (!inner_map_meta) {
 		fdput(f);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b155cd17c1bd..ebf0a673cb83 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -463,7 +463,7 @@ int map_check_no_btf(const struct bpf_map *map,
 	return -ENOTSUPP;
 }
 
-static int map_check_btf(const struct bpf_map *map, const struct btf *btf,
+static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			 u32 btf_key_id, u32 btf_value_id)
 {
 	const struct btf_type *key_type, *value_type;
@@ -478,6 +478,21 @@ static int map_check_btf(const struct bpf_map *map, const struct btf *btf,
 	if (!value_type || value_size != map->value_size)
 		return -EINVAL;
 
+	map->spin_lock_off = btf_find_spin_lock(btf, value_type);
+
+	if (map_value_has_spin_lock(map)) {
+		if (map->map_type != BPF_MAP_TYPE_HASH &&
+		    map->map_type != BPF_MAP_TYPE_ARRAY)
+			return -ENOTSUPP;
+		if (map->spin_lock_off + sizeof(struct bpf_spin_lock) >
+		    map->value_size) {
+			WARN_ONCE(1,
+				  "verifier bug spin_lock_off %d value_size %d\n",
+				  map->spin_lock_off, map->value_size);
+			return -EFAULT;
+		}
+	}
+
 	if (map->ops->map_check_btf)
 		ret = map->ops->map_check_btf(map, btf, key_type, value_type);
 
@@ -542,6 +557,8 @@ static int map_create(union bpf_attr *attr)
 		map->btf = btf;
 		map->btf_key_type_id = attr->btf_key_type_id;
 		map->btf_value_type_id = attr->btf_value_type_id;
+	} else {
+		map->spin_lock_off = -EINVAL;
 	}
 
 	err = security_bpf_map_alloc(map);
@@ -740,7 +757,7 @@ static int map_lookup_elem(union bpf_attr *attr)
 			err = -ENOENT;
 		} else {
 			err = 0;
-			memcpy(value, ptr, value_size);
+			copy_map_value(map, value, ptr);
 		}
 		rcu_read_unlock();
 	}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ce87198ecd01..cf636b07faf6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -213,6 +213,7 @@ struct bpf_call_arg_meta {
 	s64 msize_smax_value;
 	u64 msize_umax_value;
 	int ptr_id;
+	int func_id;
 };
 
 static DEFINE_MUTEX(bpf_verifier_lock);
@@ -351,6 +352,12 @@ static bool reg_is_refcounted(const struct bpf_reg_state *reg)
 	return type_is_refcounted(reg->type);
 }
 
+static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
+{
+	return reg->type == PTR_TO_MAP_VALUE &&
+		map_value_has_spin_lock(reg->map_ptr);
+}
+
 static bool reg_is_refcounted_or_null(const struct bpf_reg_state *reg)
 {
 	return type_is_refcounted_or_null(reg->type);
@@ -712,6 +719,7 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 	}
 	dst_state->speculative = src->speculative;
 	dst_state->curframe = src->curframe;
+	dst_state->active_spin_lock = src->active_spin_lock;
 	for (i = 0; i <= src->curframe; i++) {
 		dst = dst_state->frame[i];
 		if (!dst) {
@@ -1483,6 +1491,21 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 	if (err)
 		verbose(env, "R%d max value is outside of the array range\n",
 			regno);
+
+	if (map_value_has_spin_lock(reg->map_ptr)) {
+		u32 lock = reg->map_ptr->spin_lock_off;
+
+		/* if any part of struct bpf_spin_lock can be touched by
+		 * load/store reject this program
+		 */
+		if ((reg->smin_value + off <= lock &&
+		     lock < reg->umax_value + off + size) ||
+		    (reg->smin_value + off < lock + sizeof(struct bpf_spin_lock) &&
+		     lock + sizeof(struct bpf_spin_lock) <= reg->umax_value + off + size)) {
+			verbose(env, "bpf_spin_lock cannot be accessed directly by load/store\n");
+			return -EACCES;
+		}
+	}
 	return err;
 }
 
@@ -2192,6 +2215,91 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
 	}
 }
 
+/* Implementation details:
+ * bpf_map_lookup returns PTR_TO_MAP_VALUE_OR_NULL
+ * Two bpf_map_lookups (even with the same key) will have different reg->id.
+ * For traditional PTR_TO_MAP_VALUE the verifier clears reg->id after
+ * value_or_null->value transition, since the verifier only cares about
+ * the range of access to valid map value pointer and doesn't care about actual
+ * address of the map element.
+ * For maps with 'struct bpf_spin_lock' inside map value the verifier keeps
+ * reg->id > 0 after value_or_null->value transition. By doing so
+ * two bpf_map_lookups will be considered two different pointers that
+ * point to different bpf_spin_locks.
+ * The verifier allows taking only one bpf_spin_lock at a time to avoid
+ * dead-locks.
+ * Since only one bpf_spin_lock is allowed the checks are simpler than
+ * reg_is_refcounted() logic. The verifier needs to remember only
+ * one spin_lock instead of array of acquired_refs.
+ * cur_state->active_spin_lock remembers which map value element got locked
+ * and clears it after bpf_spin_unlock.
+ */
+static int process_spin_lock(struct bpf_verifier_env *env, int regno,
+			     bool is_lock)
+{
+	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
+	struct bpf_verifier_state *cur = env->cur_state;
+	bool is_const = tnum_is_const(reg->var_off);
+	struct bpf_map *map = reg->map_ptr;
+	u64 val = reg->var_off.value;
+
+	if (reg->type != PTR_TO_MAP_VALUE) {
+		verbose(env, "R%d is not a pointer to map_value\n", regno);
+		return -EINVAL;
+	}
+	if (!is_const) {
+		verbose(env,
+			"R%d doesn't have constant offset. bpf_spin_lock has to be at the constant offset\n",
+			regno);
+		return -EINVAL;
+	}
+	if (!map->btf) {
+		verbose(env,
+			"map '%s' has to have BTF in order to use bpf_spin_lock\n",
+			map->name);
+		return -EINVAL;
+	}
+	if (!map_value_has_spin_lock(map)) {
+		if (map->spin_lock_off == -E2BIG)
+			verbose(env,
+				"map '%s' has more than one 'struct bpf_spin_lock'\n",
+				map->name);
+		else if (map->spin_lock_off == -ENOENT)
+			verbose(env,
+				"map '%s' doesn't have 'struct bpf_spin_lock'\n",
+				map->name);
+		else
+			verbose(env,
+				"map '%s' is not a struct type or bpf_spin_lock is mangled\n",
+				map->name);
+		return -EINVAL;
+	}
+	if (map->spin_lock_off != val + reg->off) {
+		verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock'\n",
+			val + reg->off);
+		return -EINVAL;
+	}
+	if (is_lock) {
+		if (cur->active_spin_lock) {
+			verbose(env,
+				"Locking two bpf_spin_locks are not allowed\n");
+			return -EINVAL;
+		}
+		cur->active_spin_lock = reg->id;
+	} else {
+		if (!cur->active_spin_lock) {
+			verbose(env, "bpf_spin_unlock without taking a lock\n");
+			return -EINVAL;
+		}
+		if (cur->active_spin_lock != reg->id) {
+			verbose(env, "bpf_spin_unlock of different lock\n");
+			return -EINVAL;
+		}
+		cur->active_spin_lock = 0;
+	}
+	return 0;
+}
+
 static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
 {
 	return type == ARG_PTR_TO_MEM ||
@@ -2268,6 +2376,17 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 			return -EFAULT;
 		}
 		meta->ptr_id = reg->id;
+	} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
+		if (meta->func_id == BPF_FUNC_spin_lock) {
+			if (process_spin_lock(env, regno, true))
+				return -EACCES;
+		} else if (meta->func_id == BPF_FUNC_spin_unlock) {
+			if (process_spin_lock(env, regno, false))
+				return -EACCES;
+		} else {
+			verbose(env, "verifier internal error\n");
+			return -EFAULT;
+		}
 	} else if (arg_type_is_mem_ptr(arg_type)) {
 		expected_type = PTR_TO_STACK;
 		/* One exception here. In case function allows for NULL to be
@@ -2887,6 +3006,7 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 		return err;
 	}
 
+	meta.func_id = func_id;
 	/* check args */
 	err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
 	if (err)
@@ -4344,7 +4464,8 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
 		} else if (reg->type == PTR_TO_SOCKET_OR_NULL) {
 			reg->type = PTR_TO_SOCKET;
 		}
-		if (is_null || !reg_is_refcounted(reg)) {
+		if (is_null || !(reg_is_refcounted(reg) ||
+				 reg_may_point_to_spin_lock(reg))) {
 			/* We don't need id from this point onwards anymore,
 			 * thus we should better reset it, so that state
 			 * pruning has chances to take effect.
@@ -4713,6 +4834,11 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return err;
 	}
 
+	if (env->cur_state->active_spin_lock) {
+		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
+		return -EINVAL;
+	}
+
 	if (regs[BPF_REG_6].type != PTR_TO_CTX) {
 		verbose(env,
 			"at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
@@ -5448,8 +5574,11 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
 	case PTR_TO_MAP_VALUE:
 		/* If the new min/max/var_off satisfy the old ones and
 		 * everything else matches, we are OK.
-		 * We don't care about the 'id' value, because nothing
-		 * uses it for PTR_TO_MAP_VALUE (only for ..._OR_NULL)
+		 * 'id' is not compared, since it's only used for maps with
+		 * bpf_spin_lock inside map element and in such cases if
+		 * the rest of the prog is valid for one map element then
+		 * it's valid for all map elements regardless of the key
+		 * used in bpf_map_lookup()
 		 */
 		return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 &&
 		       range_within(rold, rcur) &&
@@ -5652,6 +5781,9 @@ static bool states_equal(struct bpf_verifier_env *env,
 	if (old->speculative && !cur->speculative)
 		return false;
 
+	if (old->active_spin_lock != cur->active_spin_lock)
+		return false;
+
 	/* for states to be equal callsites have to be the same
 	 * and all frame states need to be equivalent
 	 */
@@ -6069,6 +6201,12 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
+				if (env->cur_state->active_spin_lock &&
+				    (insn->src_reg == BPF_PSEUDO_CALL ||
+				     insn->imm != BPF_FUNC_spin_unlock)) {
+					verbose(env, "function calls are not allowed while holding a lock\n");
+					return -EINVAL;
+				}
 				if (insn->src_reg == BPF_PSEUDO_CALL)
 					err = check_func_call(env, insn, &env->insn_idx);
 				else
@@ -6097,6 +6235,11 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
+				if (env->cur_state->active_spin_lock) {
+					verbose(env, "bpf_spin_unlock is missing\n");
+					return -EINVAL;
+				}
+
 				if (state->curframe) {
 					/* exit from nested function */
 					env->prev_insn_idx = env->insn_idx;
diff --git a/net/core/filter.c b/net/core/filter.c
index 2b3b436ef545..24a5d874d156 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5306,10 +5306,20 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_tail_call_proto;
 	case BPF_FUNC_ktime_get_ns:
 		return &bpf_ktime_get_ns_proto;
+	default:
+		break;
+	}
+
+	if (!capable(CAP_SYS_ADMIN))
+		return NULL;
+
+	switch (func_id) {
+	case BPF_FUNC_spin_lock:
+		return &bpf_spin_lock_proto;
+	case BPF_FUNC_spin_unlock:
+		return &bpf_spin_unlock_proto;
 	case BPF_FUNC_trace_printk:
-		if (capable(CAP_SYS_ADMIN))
-			return bpf_get_trace_printk_proto();
-		/* else: fall through */
+		return bpf_get_trace_printk_proto();
 	default:
 		return NULL;
 	}
-- 
2.17.1