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bpf: add program side {rd, wr}only support for maps
This work adds two new map creation flags BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG in order to allow for read-only or write-only BPF maps from a BPF program side. Today we have BPF_F_RDONLY and BPF_F_WRONLY, but this only applies to system call side, meaning the BPF program has full read/write access to the map as usual while bpf(2) calls with map fd can either only read or write into the map depending on the flags. BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG allows for the exact opposite such that verifier is going to reject program loads if write into a read-only map or a read into a write-only map is detected. For read-only map case also some helpers are forbidden for programs that would alter the map state such as map deletion, update, etc. As opposed to the two BPF_F_RDONLY / BPF_F_WRONLY flags, BPF_F_RDONLY_PROG as well as BPF_F_WRONLY_PROG really do correspond to the map lifetime. We've enabled this generic map extension to various non-special maps holding normal user data: array, hash, lru, lpm, local storage, queue and stack. Further generic map types could be followed up in future depending on use-case. Main use case here is to forbid writes into .rodata map values from verifier side. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -430,6 +430,35 @@ struct bpf_array {
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#define BPF_COMPLEXITY_LIMIT_INSNS 1000000 /* yes. 1M insns */
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#define MAX_TAIL_CALL_CNT 32
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#define BPF_F_ACCESS_MASK (BPF_F_RDONLY | \
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BPF_F_RDONLY_PROG | \
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BPF_F_WRONLY | \
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BPF_F_WRONLY_PROG)
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#define BPF_MAP_CAN_READ BIT(0)
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#define BPF_MAP_CAN_WRITE BIT(1)
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static inline u32 bpf_map_flags_to_cap(struct bpf_map *map)
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{
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u32 access_flags = map->map_flags & (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
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/* Combination of BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG is
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* not possible.
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*/
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if (access_flags & BPF_F_RDONLY_PROG)
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return BPF_MAP_CAN_READ;
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else if (access_flags & BPF_F_WRONLY_PROG)
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return BPF_MAP_CAN_WRITE;
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else
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return BPF_MAP_CAN_READ | BPF_MAP_CAN_WRITE;
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}
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static inline bool bpf_map_flags_access_ok(u32 access_flags)
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{
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return (access_flags & (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG)) !=
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(BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
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}
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struct bpf_event_entry {
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struct perf_event *event;
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struct file *perf_file;
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@ -294,7 +294,7 @@ enum bpf_attach_type {
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#define BPF_OBJ_NAME_LEN 16U
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/* Flags for accessing BPF object */
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/* Flags for accessing BPF object from syscall side. */
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#define BPF_F_RDONLY (1U << 3)
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#define BPF_F_WRONLY (1U << 4)
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@ -304,6 +304,10 @@ enum bpf_attach_type {
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/* Zero-initialize hash function seed. This should only be used for testing. */
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#define BPF_F_ZERO_SEED (1U << 6)
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/* Flags for accessing BPF object from program side. */
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#define BPF_F_RDONLY_PROG (1U << 7)
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#define BPF_F_WRONLY_PROG (1U << 8)
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/* flags for BPF_PROG_QUERY */
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#define BPF_F_QUERY_EFFECTIVE (1U << 0)
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@ -22,7 +22,7 @@
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#include "map_in_map.h"
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#define ARRAY_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
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(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
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static void bpf_array_free_percpu(struct bpf_array *array)
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{
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@ -63,6 +63,7 @@ int array_map_alloc_check(union bpf_attr *attr)
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if (attr->max_entries == 0 || attr->key_size != 4 ||
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attr->value_size == 0 ||
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attr->map_flags & ~ARRAY_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags) ||
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(percpu && numa_node != NUMA_NO_NODE))
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return -EINVAL;
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@ -472,6 +473,9 @@ static int fd_array_map_alloc_check(union bpf_attr *attr)
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/* only file descriptors can be stored in this type of map */
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if (attr->value_size != sizeof(u32))
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return -EINVAL;
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/* Program read-only/write-only not supported for special maps yet. */
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if (attr->map_flags & (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG))
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return -EINVAL;
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return array_map_alloc_check(attr);
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}
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@ -23,7 +23,7 @@
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#define HTAB_CREATE_FLAG_MASK \
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(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE | \
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BPF_F_RDONLY | BPF_F_WRONLY | BPF_F_ZERO_SEED)
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BPF_F_ACCESS_MASK | BPF_F_ZERO_SEED)
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struct bucket {
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struct hlist_nulls_head head;
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@ -262,8 +262,8 @@ static int htab_map_alloc_check(union bpf_attr *attr)
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/* Guard against local DoS, and discourage production use. */
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return -EPERM;
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if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK)
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/* reserved bits should not be used */
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if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags))
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return -EINVAL;
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if (!lru && percpu_lru)
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@ -14,7 +14,7 @@ DEFINE_PER_CPU(struct bpf_cgroup_storage*, bpf_cgroup_storage[MAX_BPF_CGROUP_STO
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#ifdef CONFIG_CGROUP_BPF
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#define LOCAL_STORAGE_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
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(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
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struct bpf_cgroup_storage_map {
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struct bpf_map map;
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@ -282,8 +282,8 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
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if (attr->value_size > PAGE_SIZE)
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return ERR_PTR(-E2BIG);
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if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK)
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/* reserved bits should not be used */
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if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags))
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return ERR_PTR(-EINVAL);
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if (attr->max_entries)
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@ -538,7 +538,7 @@ out:
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#define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)
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#define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \
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BPF_F_RDONLY | BPF_F_WRONLY)
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BPF_F_ACCESS_MASK)
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static struct bpf_map *trie_alloc(union bpf_attr *attr)
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{
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@ -553,6 +553,7 @@ static struct bpf_map *trie_alloc(union bpf_attr *attr)
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if (attr->max_entries == 0 ||
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!(attr->map_flags & BPF_F_NO_PREALLOC) ||
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attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags) ||
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attr->key_size < LPM_KEY_SIZE_MIN ||
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attr->key_size > LPM_KEY_SIZE_MAX ||
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attr->value_size < LPM_VAL_SIZE_MIN ||
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@ -11,8 +11,7 @@
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#include "percpu_freelist.h"
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#define QUEUE_STACK_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
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(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
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struct bpf_queue_stack {
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struct bpf_map map;
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@ -52,7 +51,8 @@ static int queue_stack_map_alloc_check(union bpf_attr *attr)
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 0 ||
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attr->value_size == 0 ||
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attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
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attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags))
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return -EINVAL;
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if (attr->value_size > KMALLOC_MAX_SIZE)
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@ -501,6 +501,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
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map->spin_lock_off = btf_find_spin_lock(btf, value_type);
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if (map_value_has_spin_lock(map)) {
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if (map->map_flags & BPF_F_RDONLY_PROG)
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return -EACCES;
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if (map->map_type != BPF_MAP_TYPE_HASH &&
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map->map_type != BPF_MAP_TYPE_ARRAY &&
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map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE)
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@ -1439,6 +1439,28 @@ static int check_stack_access(struct bpf_verifier_env *env,
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return 0;
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}
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static int check_map_access_type(struct bpf_verifier_env *env, u32 regno,
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int off, int size, enum bpf_access_type type)
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{
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struct bpf_reg_state *regs = cur_regs(env);
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struct bpf_map *map = regs[regno].map_ptr;
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u32 cap = bpf_map_flags_to_cap(map);
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if (type == BPF_WRITE && !(cap & BPF_MAP_CAN_WRITE)) {
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verbose(env, "write into map forbidden, value_size=%d off=%d size=%d\n",
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map->value_size, off, size);
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return -EACCES;
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}
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if (type == BPF_READ && !(cap & BPF_MAP_CAN_READ)) {
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verbose(env, "read from map forbidden, value_size=%d off=%d size=%d\n",
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map->value_size, off, size);
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return -EACCES;
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}
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return 0;
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}
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/* check read/write into map element returned by bpf_map_lookup_elem() */
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static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
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int size, bool zero_size_allowed)
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@ -2024,7 +2046,9 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
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verbose(env, "R%d leaks addr into map\n", value_regno);
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return -EACCES;
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}
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err = check_map_access_type(env, regno, off, size, t);
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if (err)
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return err;
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err = check_map_access(env, regno, off, size, false);
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if (!err && t == BPF_READ && value_regno >= 0)
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mark_reg_unknown(env, regs, value_regno);
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@ -2327,6 +2351,10 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
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return check_packet_access(env, regno, reg->off, access_size,
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zero_size_allowed);
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case PTR_TO_MAP_VALUE:
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if (check_map_access_type(env, regno, reg->off, access_size,
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meta && meta->raw_mode ? BPF_WRITE :
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BPF_READ))
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return -EACCES;
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return check_map_access(env, regno, reg->off, access_size,
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zero_size_allowed);
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default: /* scalar_value|ptr_to_stack or invalid ptr */
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@ -3059,6 +3087,7 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
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int func_id, int insn_idx)
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{
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struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
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struct bpf_map *map = meta->map_ptr;
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if (func_id != BPF_FUNC_tail_call &&
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func_id != BPF_FUNC_map_lookup_elem &&
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@ -3069,11 +3098,24 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
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func_id != BPF_FUNC_map_peek_elem)
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return 0;
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if (meta->map_ptr == NULL) {
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if (map == NULL) {
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verbose(env, "kernel subsystem misconfigured verifier\n");
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return -EINVAL;
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}
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/* In case of read-only, some additional restrictions
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* need to be applied in order to prevent altering the
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* state of the map from program side.
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*/
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if ((map->map_flags & BPF_F_RDONLY_PROG) &&
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(func_id == BPF_FUNC_map_delete_elem ||
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func_id == BPF_FUNC_map_update_elem ||
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func_id == BPF_FUNC_map_push_elem ||
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func_id == BPF_FUNC_map_pop_elem)) {
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verbose(env, "write into map forbidden\n");
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return -EACCES;
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}
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if (!BPF_MAP_PTR(aux->map_state))
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bpf_map_ptr_store(aux, meta->map_ptr,
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meta->map_ptr->unpriv_array);
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