Replace deprecated 0-length array in struct bpf_lpm_trie_key with
flexible array. Found with GCC 13:
../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=]
207 | *(__be16 *)&key->data[i]);
| ^~~~~~~~~~~~~
../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16'
102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
| ^
../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu'
97 | #define be16_to_cpu __be16_to_cpu
| ^~~~~~~~~~~~~
../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu'
206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i]
^
| ^~~~~~~~~~~
In file included from ../include/linux/bpf.h:7:
../include/uapi/linux/bpf.h:82:17: note: while referencing 'data'
82 | __u8 data[0]; /* Arbitrary size */
| ^~~~
And found at run-time under CONFIG_FORTIFY_SOURCE:
UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49
index 0 is out of range for type '__u8 [*]'
Changing struct bpf_lpm_trie_key is difficult since has been used by
userspace. For example, in Cilium:
struct egress_gw_policy_key {
struct bpf_lpm_trie_key lpm_key;
__u32 saddr;
__u32 daddr;
};
While direct references to the "data" member haven't been found, there
are static initializers what include the final member. For example,
the "{}" here:
struct egress_gw_policy_key in_key = {
.lpm_key = { 32 + 24, {} },
.saddr = CLIENT_IP,
.daddr = EXTERNAL_SVC_IP & 0Xffffff,
};
To avoid the build time and run time warnings seen with a 0-sized
trailing array for struct bpf_lpm_trie_key, introduce a new struct
that correctly uses a flexible array for the trailing bytes,
struct bpf_lpm_trie_key_u8. As part of this, include the "header"
portion (which is just the "prefixlen" member), so it can be used
by anything building a bpf_lpr_trie_key that has trailing members that
aren't a u8 flexible array (like the self-test[1]), which is named
struct bpf_lpm_trie_key_hdr.
Unfortunately, C++ refuses to parse the __struct_group() helper, so
it is not possible to define struct bpf_lpm_trie_key_hdr directly in
struct bpf_lpm_trie_key_u8, so we must open-code the union directly.
Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out,
and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment
to the UAPI header directing folks to the two new options.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Closes: https://paste.debian.net/hidden/ca500597/
Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/
Link: https://lore.kernel.org/bpf/20240222155612.it.533-kees@kernel.org
LPM tries may be created with a maximum prefix length that is a multiple
of 8, in the range from 8 to 2048. The key used for lookup and update
-operations is a ``struct bpf_lpm_trie_key``, extended by
+operations is a ``struct bpf_lpm_trie_key_u8``, extended by
``max_prefixlen/8`` bytes.
- For IPv4 addresses the data length is 4 bytes
__s32 imm; /* signed immediate constant */
};
-/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */
+/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for
+ * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for
+ * the trailing flexible array member) instead.
+ */
struct bpf_lpm_trie_key {
__u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */
__u8 data[0]; /* Arbitrary size */
};
+/* Header for bpf_lpm_trie_key structs */
+struct bpf_lpm_trie_key_hdr {
+ __u32 prefixlen;
+};
+
+/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */
+struct bpf_lpm_trie_key_u8 {
+ union {
+ struct bpf_lpm_trie_key_hdr hdr;
+ __u32 prefixlen;
+ };
+ __u8 data[]; /* Arbitrary size */
+};
+
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
__u32 attach_type; /* program attach type (enum bpf_attach_type) */
*/
static size_t longest_prefix_match(const struct lpm_trie *trie,
const struct lpm_trie_node *node,
- const struct bpf_lpm_trie_key *key)
+ const struct bpf_lpm_trie_key_u8 *key)
{
u32 limit = min(node->prefixlen, key->prefixlen);
u32 prefixlen = 0, i = 0;
BUILD_BUG_ON(offsetof(struct lpm_trie_node, data) % sizeof(u32));
- BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key, data) % sizeof(u32));
+ BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key_u8, data) % sizeof(u32));
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(CONFIG_64BIT)
{
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
struct lpm_trie_node *node, *found = NULL;
- struct bpf_lpm_trie_key *key = _key;
+ struct bpf_lpm_trie_key_u8 *key = _key;
if (key->prefixlen > trie->max_prefixlen)
return NULL;
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL;
struct lpm_trie_node __rcu **slot;
- struct bpf_lpm_trie_key *key = _key;
+ struct bpf_lpm_trie_key_u8 *key = _key;
unsigned long irq_flags;
unsigned int next_bit;
size_t matchlen = 0;
static long trie_delete_elem(struct bpf_map *map, void *_key)
{
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
- struct bpf_lpm_trie_key *key = _key;
+ struct bpf_lpm_trie_key_u8 *key = _key;
struct lpm_trie_node __rcu **trim, **trim2;
struct lpm_trie_node *node, *parent;
unsigned long irq_flags;
sizeof(struct lpm_trie_node))
#define LPM_VAL_SIZE_MIN 1
-#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key) + (X))
+#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key_u8) + (X))
#define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)
#define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)
/* copy mandatory map attributes */
bpf_map_init_from_attr(&trie->map, attr);
trie->data_size = attr->key_size -
- offsetof(struct bpf_lpm_trie_key, data);
+ offsetof(struct bpf_lpm_trie_key_u8, data);
trie->max_prefixlen = trie->data_size * 8;
spin_lock_init(&trie->lock);
{
struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
- struct bpf_lpm_trie_key *key = _key, *next_key = _next_key;
+ struct bpf_lpm_trie_key_u8 *key = _key, *next_key = _next_key;
struct lpm_trie_node **node_stack = NULL;
int err = 0, stack_ptr = -1;
unsigned int next_bit;
}
do_copy:
next_key->prefixlen = next_node->prefixlen;
- memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data),
+ memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key_u8, data),
next_node->data, trie->data_size);
free_stack:
kfree(node_stack);
const struct btf_type *key_type,
const struct btf_type *value_type)
{
- /* Keys must have struct bpf_lpm_trie_key embedded. */
+ /* Keys must have struct bpf_lpm_trie_key_u8 embedded. */
return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ?
-EINVAL : 0;
}
static void fill_lpm_trie(void)
{
- struct bpf_lpm_trie_key *key;
+ struct bpf_lpm_trie_key_u8 *key;
unsigned long value = 0;
unsigned int i;
int r;
static void read_route(struct nlmsghdr *nh, int nll)
{
char dsts[24], gws[24], ifs[16], dsts_len[24], metrics[24];
- struct bpf_lpm_trie_key *prefix_key;
+ struct bpf_lpm_trie_key_u8 *prefix_key;
struct rtattr *rt_attr;
struct rtmsg *rt_msg;
int rtm_family;
__s32 imm; /* signed immediate constant */
};
-/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */
+/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for
+ * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for
+ * the trailing flexible array member) instead.
+ */
struct bpf_lpm_trie_key {
__u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */
__u8 data[0]; /* Arbitrary size */
};
+/* Header for bpf_lpm_trie_key structs */
+struct bpf_lpm_trie_key_hdr {
+ __u32 prefixlen;
+};
+
+/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */
+struct bpf_lpm_trie_key_u8 {
+ union {
+ struct bpf_lpm_trie_key_hdr hdr;
+ __u32 prefixlen;
+ };
+ __u8 data[]; /* Arbitrary size */
+};
+
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
__u32 attach_type; /* program attach type (enum bpf_attach_type) */
} __attribute__((preserve_access_index));
struct lpm_key {
- struct bpf_lpm_trie_key trie_key;
+ struct bpf_lpm_trie_key_hdr trie_key;
__u32 data;
};
volatile size_t n_matches, n_matches_after_delete;
size_t i, j, n_nodes, n_lookups;
struct tlpm_node *t, *list = NULL;
- struct bpf_lpm_trie_key *key;
+ struct bpf_lpm_trie_key_u8 *key;
uint8_t *data, *value;
int r, map;
static void test_lpm_ipaddr(void)
{
LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC);
- struct bpf_lpm_trie_key *key_ipv4;
- struct bpf_lpm_trie_key *key_ipv6;
+ struct bpf_lpm_trie_key_u8 *key_ipv4;
+ struct bpf_lpm_trie_key_u8 *key_ipv6;
size_t key_size_ipv4;
size_t key_size_ipv6;
int map_fd_ipv4;
static void test_lpm_delete(void)
{
LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC);
- struct bpf_lpm_trie_key *key;
+ struct bpf_lpm_trie_key_u8 *key;
size_t key_size;
int map_fd;
__u64 value;
static void test_lpm_get_next_key(void)
{
LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC);
- struct bpf_lpm_trie_key *key_p, *next_key_p;
+ struct bpf_lpm_trie_key_u8 *key_p, *next_key_p;
size_t key_size;
__u32 value = 0;
int map_fd;
{
int i, j, ret, iter, key_size;
struct lpm_mt_test_info *info = arg;
- struct bpf_lpm_trie_key *key_p;
+ struct bpf_lpm_trie_key_u8 *key_p;
- key_size = sizeof(struct bpf_lpm_trie_key) + sizeof(__u32);
+ key_size = sizeof(*key_p) + sizeof(__u32);
key_p = alloca(key_size);
for (iter = 0; iter < info->iter; iter++)
for (i = 0; i < MAX_TEST_KEYS; i++) {
ret = bpf_map_lookup_elem(info->map_fd, key_p, &value);
assert(ret == 0 || errno == ENOENT);
} else {
- struct bpf_lpm_trie_key *next_key_p = alloca(key_size);
+ struct bpf_lpm_trie_key_u8 *next_key_p = alloca(key_size);
ret = bpf_map_get_next_key(info->map_fd, key_p, next_key_p);
assert(ret == 0 || errno == ENOENT || errno == ENOMEM);
}
/* create a trie */
value_size = sizeof(__u32);
- key_size = sizeof(struct bpf_lpm_trie_key) + value_size;
+ key_size = sizeof(struct bpf_lpm_trie_key_hdr) + value_size;
map_fd = bpf_map_create(BPF_MAP_TYPE_LPM_TRIE, NULL, key_size, value_size, 100, &opts);
/* create 4 threads to test update, delete, lookup and get_next_key */
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