Merge branch 'check-bloom-filter-map-value-size'

Andrei Matei says:

====================
Check bloom filter map value size

v1->v2:
- prepend a patch addressing the bloom map specifically
- change low-level rejection error to EFAULT, to indicate a bug
====================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Alexei Starovoitov

kernel/bpf/bloom_filter.c

@@ -80,6 +80,18 @@ static int bloom_map_get_next_key(struct bpf_map *map, void *key, void *next_key
 	return -EOPNOTSUPP;
 }
 
+/* Called from syscall */
+static int bloom_map_alloc_check(union bpf_attr *attr)
+{
+	if (attr->value_size > KMALLOC_MAX_SIZE)
+		/* if value_size is bigger, the user space won't be able to
+		 * access the elements.
+		 */
+		return -E2BIG;
+
+	return 0;
+}
+
 static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
 {
 	u32 bitset_bytes, bitset_mask, nr_hash_funcs, nr_bits;
@@ -191,6 +203,7 @@ static u64 bloom_map_mem_usage(const struct bpf_map *map)
 BTF_ID_LIST_SINGLE(bpf_bloom_map_btf_ids, struct, bpf_bloom_filter)
 const struct bpf_map_ops bloom_filter_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
+	.map_alloc_check = bloom_map_alloc_check,
 	.map_alloc = bloom_map_alloc,
 	.map_free = bloom_map_free,
 	.map_get_next_key = bloom_map_get_next_key,

kernel/bpf/verifier.c

@@ -6701,6 +6701,11 @@ static int check_stack_access_within_bounds(
 	err = check_stack_slot_within_bounds(env, min_off, state, type);
 	if (!err && max_off > 0)
 		err = -EINVAL; /* out of stack access into non-negative offsets */
+	if (!err && access_size < 0)
+		/* access_size should not be negative (or overflow an int); others checks
+		 * along the way should have prevented such an access.
+		 */
+		err = -EFAULT; /* invalid negative access size; integer overflow? */
 
 	if (err) {
 		if (tnum_is_const(reg->var_off)) {

tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c

@@ -2,6 +2,7 @@
 /* Copyright (c) 2021 Facebook */
 
 #include <sys/syscall.h>
+#include <limits.h>
 #include <test_progs.h>
 #include "bloom_filter_map.skel.h"
 
@@ -21,6 +22,11 @@ static void test_fail_cases(void)
 	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid value size 0"))
 		close(fd);
 
+	/* Invalid value size: too big */
+	fd = bpf_map_create(BPF_MAP_TYPE_BLOOM_FILTER, NULL, 0, INT32_MAX, 100, NULL);
+	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid value too large"))
+		close(fd);
+
 	/* Invalid max entries size */
 	fd = bpf_map_create(BPF_MAP_TYPE_BLOOM_FILTER, NULL, 0, sizeof(value), 0, NULL);
 	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid max entries size"))