Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2018-01-09

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) Prevent out-of-bounds speculation in BPF maps by masking the
   index after bounds checks in order to fix spectre v1, and
   add an option BPF_JIT_ALWAYS_ON into Kconfig that allows for
   removing the BPF interpreter from the kernel in favor of
   JIT-only mode to make spectre v2 harder, from Alexei.

2) Remove false sharing of map refcount with max_entries which
   was used in spectre v1, from Daniel.

3) Add a missing NULL psock check in sockmap in order to fix
   a race, from John.

4) Fix test_align BPF selftest case since a recent change in
   verifier rejects the bit-wise arithmetic on pointers
   earlier but test_align update was missing, from Alexei.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 100 insertions, 13 deletions

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 7c25426d3cf5..aaa319848e7d 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -53,9 +53,10 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 {
 	bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
 	int numa_node = bpf_map_attr_numa_node(attr);
+	u32 elem_size, index_mask, max_entries;
+	bool unpriv = !capable(CAP_SYS_ADMIN);
 	struct bpf_array *array;
 	u64 array_size;
-	u32 elem_size;
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
@@ -72,11 +73,20 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 
 	elem_size = round_up(attr->value_size, 8);
 
+	max_entries = attr->max_entries;
+	index_mask = roundup_pow_of_two(max_entries) - 1;
+
+	if (unpriv)
+		/* round up array size to nearest power of 2,
+		 * since cpu will speculate within index_mask limits
+		 */
+		max_entries = index_mask + 1;
+
 	array_size = sizeof(*array);
 	if (percpu)
-		array_size += (u64) attr->max_entries * sizeof(void *);
+		array_size += (u64) max_entries * sizeof(void *);
 	else
-		array_size += (u64) attr->max_entries * elem_size;
+		array_size += (u64) max_entries * elem_size;
 
 	/* make sure there is no u32 overflow later in round_up() */
 	if (array_size >= U32_MAX - PAGE_SIZE)
@@ -86,6 +96,8 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 	array = bpf_map_area_alloc(array_size, numa_node);
 	if (!array)
 		return ERR_PTR(-ENOMEM);
+	array->index_mask = index_mask;
+	array->map.unpriv_array = unpriv;
 
 	/* copy mandatory map attributes */
 	array->map.map_type = attr->map_type;
@@ -121,12 +133,13 @@ static void *array_map_lookup_elem(struct bpf_map *map, void *key)
 	if (unlikely(index >= array->map.max_entries))
 		return NULL;
 
-	return array->value + array->elem_size * index;
+	return array->value + array->elem_size * (index & array->index_mask);
 }
 
 /* emit BPF instructions equivalent to C code of array_map_lookup_elem() */
 static u32 array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 {
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	struct bpf_insn *insn = insn_buf;
 	u32 elem_size = round_up(map->value_size, 8);
 	const int ret = BPF_REG_0;
@@ -135,7 +148,12 @@ static u32 array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 
 	*insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
 	*insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
-	*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 3);
+	if (map->unpriv_array) {
+		*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 4);
+		*insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
+	} else {
+		*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 3);
+	}
 
 	if (is_power_of_2(elem_size)) {
 		*insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
@@ -157,7 +175,7 @@ static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key)
 	if (unlikely(index >= array->map.max_entries))
 		return NULL;
 
-	return this_cpu_ptr(array->pptrs[index]);
+	return this_cpu_ptr(array->pptrs[index & array->index_mask]);
 }
 
 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
@@ -177,7 +195,7 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
 	 */
 	size = round_up(map->value_size, 8);
 	rcu_read_lock();
-	pptr = array->pptrs[index];
+	pptr = array->pptrs[index & array->index_mask];
 	for_each_possible_cpu(cpu) {
 		bpf_long_memcpy(value + off, per_cpu_ptr(pptr, cpu), size);
 		off += size;
@@ -225,10 +243,11 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 		return -EEXIST;
 
 	if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
-		memcpy(this_cpu_ptr(array->pptrs[index]),
+		memcpy(this_cpu_ptr(array->pptrs[index & array->index_mask]),
 		       value, map->value_size);
 	else
-		memcpy(array->value + array->elem_size * index,
+		memcpy(array->value +
+		       array->elem_size * (index & array->index_mask),
 		       value, map->value_size);
 	return 0;
 }
@@ -262,7 +281,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	 */
 	size = round_up(map->value_size, 8);
 	rcu_read_lock();
-	pptr = array->pptrs[index];
+	pptr = array->pptrs[index & array->index_mask];
 	for_each_possible_cpu(cpu) {
 		bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value + off, size);
 		off += size;
@@ -613,6 +632,7 @@ static void *array_of_map_lookup_elem(struct bpf_map *map, void *key)
 static u32 array_of_map_gen_lookup(struct bpf_map *map,
 				   struct bpf_insn *insn_buf)
 {
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	u32 elem_size = round_up(map->value_size, 8);
 	struct bpf_insn *insn = insn_buf;
 	const int ret = BPF_REG_0;
@@ -621,7 +641,12 @@ static u32 array_of_map_gen_lookup(struct bpf_map *map,
 
 	*insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
 	*insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
-	*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
+	if (map->unpriv_array) {
+		*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 6);
+		*insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
+	} else {
+		*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
+	}
 	if (is_power_of_2(elem_size))
 		*insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
 	else
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 86b50aa26ee8..51ec2dda7f08 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -767,6 +767,7 @@ noinline u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 }
 EXPORT_SYMBOL_GPL(__bpf_call_base);
 
+#ifndef CONFIG_BPF_JIT_ALWAYS_ON
 /**
  *	__bpf_prog_run - run eBPF program on a given context
  *	@ctx: is the data we are operating on
@@ -1317,6 +1318,14 @@ EVAL6(PROG_NAME_LIST, 224, 256, 288, 320, 352, 384)
 EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
 };
 
+#else
+static unsigned int __bpf_prog_ret0(const void *ctx,
+				    const struct bpf_insn *insn)
+{
+	return 0;
+}
+#endif
+
 bool bpf_prog_array_compatible(struct bpf_array *array,
 			       const struct bpf_prog *fp)
 {
@@ -1364,9 +1373,13 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
  */
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 {
+#ifndef CONFIG_BPF_JIT_ALWAYS_ON
 	u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1);
 
 	fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1];
+#else
+	fp->bpf_func = __bpf_prog_ret0;
+#endif
 
 	/* eBPF JITs can rewrite the program in case constant
 	 * blinding is active. However, in case of error during
@@ -1376,6 +1389,12 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 	 */
 	if (!bpf_prog_is_dev_bound(fp->aux)) {
 		fp = bpf_int_jit_compile(fp);
+#ifdef CONFIG_BPF_JIT_ALWAYS_ON
+		if (!fp->jited) {
+			*err = -ENOTSUPP;
+			return fp;
+		}
+#endif
 	} else {
 		*err = bpf_prog_offload_compile(fp);
 		if (*err)
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 5ee2e41893d9..1712d319c2d8 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map)
 
 		write_lock_bh(&sock->sk_callback_lock);
 		psock = smap_psock_sk(sock);
-		smap_list_remove(psock, &stab->sock_map[i]);
-		smap_release_sock(psock, sock);
+		/* This check handles a racing sock event that can get the
+		 * sk_callback_lock before this case but after xchg happens
+		 * causing the refcnt to hit zero and sock user data (psock)
+		 * to be null and queued for garbage collection.
+		 */
+		if (likely(psock)) {
+			smap_list_remove(psock, &stab->sock_map[i]);
+			smap_release_sock(psock, sock);
+		}
 		write_unlock_bh(&sock->sk_callback_lock);
 	}
 	rcu_read_unlock();
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 04b24876cd23..b414d6b2d470 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1729,6 +1729,13 @@ static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
 	err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
 	if (err)
 		return err;
+	if (func_id == BPF_FUNC_tail_call) {
+		if (meta.map_ptr == NULL) {
+			verbose(env, "verifier bug\n");
+			return -EINVAL;
+		}
+		env->insn_aux_data[insn_idx].map_ptr = meta.map_ptr;
+	}
 	err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
 	if (err)
 		return err;
@@ -4456,6 +4463,35 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
 			 */
 			insn->imm = 0;
 			insn->code = BPF_JMP | BPF_TAIL_CALL;
+
+			/* instead of changing every JIT dealing with tail_call
+			 * emit two extra insns:
+			 * if (index >= max_entries) goto out;
+			 * index &= array->index_mask;
+			 * to avoid out-of-bounds cpu speculation
+			 */
+			map_ptr = env->insn_aux_data[i + delta].map_ptr;
+			if (map_ptr == BPF_MAP_PTR_POISON) {
+				verbose(env, "tail_call obusing map_ptr\n");
+				return -EINVAL;
+			}
+			if (!map_ptr->unpriv_array)
+				continue;
+			insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
+						  map_ptr->max_entries, 2);
+			insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
+						    container_of(map_ptr,
+								 struct bpf_array,
+								 map)->index_mask);
+			insn_buf[2] = *insn;
+			cnt = 3;
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+			if (!new_prog)
+				return -ENOMEM;
+
+			delta    += cnt - 1;
+			env->prog = prog = new_prog;
+			insn      = new_prog->insnsi + i + delta;
 			continue;
 		}