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bpf: factor out fetching bpf_map from FD and adding it to used_maps list

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Factor out the logic to extract bpf_map instances from FD embedded in
bpf_insns, adding it to the list of used_maps (unless it's already
there, in which case we just reuse map's index). This simplifies the
logic in resolve_pseudo_ldimm64(), especially around `struct fd`
handling, as all that is now neatly contained in the helper and doesn't
leak into a dozen error handling paths.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-08-06 14:31:34 -07:00
parent 51a1ca933f
commit 535ead44ff
1 changed files with 68 additions and 51 deletions
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117
kernel/bpf/verifier.c
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@ -18865,6 +18865,58 @@ static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
}
/* Add map behind fd to used maps list, if it's not already there, and return
* its index. Also set *reused to true if this map was already in the list of
* used maps.
* Returns <0 on error, or >= 0 index, on success.
*/
static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reused)
{
struct fd f = fdget(fd);
struct bpf_map *map;
int i;
map = __bpf_map_get(f);
if (IS_ERR(map)) {
verbose(env, "fd %d is not pointing to valid bpf_map\n", fd);
return PTR_ERR(map);
}
/* check whether we recorded this map already */
for (i = 0; i < env->used_map_cnt; i++) {
if (env->used_maps[i] == map) {
*reused = true;
fdput(f);
return i;
}
}
if (env->used_map_cnt >= MAX_USED_MAPS) {
verbose(env, "The total number of maps per program has reached the limit of %u\n",
MAX_USED_MAPS);
fdput(f);
return -E2BIG;
}
if (env->prog->sleepable)
atomic64_inc(&map->sleepable_refcnt);
/* hold the map. If the program is rejected by verifier,
* the map will be released by release_maps() or it
* will be used by the valid program until it's unloaded
* and all maps are released in bpf_free_used_maps()
*/
bpf_map_inc(map);
*reused = false;
env->used_maps[env->used_map_cnt++] = map;
fdput(f);
return env->used_map_cnt - 1;
}
/* find and rewrite pseudo imm in ld_imm64 instructions:
*
* 1. if it accesses map FD, replace it with actual map pointer.
@ -18876,7 +18928,7 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
{
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i, j, err;
int i, err;
err = bpf_prog_calc_tag(env->prog);
if (err)
@ -18893,9 +18945,10 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
struct bpf_insn_aux_data *aux;
struct bpf_map *map;
struct fd f;
int map_idx;
u64 addr;
u32 fd;
bool reused;
if (i == insn_cnt - 1 || insn[1].code != 0 ||
insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
@ -18956,20 +19009,18 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
break;
}
f = fdget(fd);
map = __bpf_map_get(f);
if (IS_ERR(map)) {
verbose(env, "fd %d is not pointing to valid bpf_map\n", fd);
return PTR_ERR(map);
}
err = check_map_prog_compatibility(env, map, env->prog);
if (err) {
fdput(f);
return err;
}
map_idx = add_used_map_from_fd(env, fd, &reused);
if (map_idx < 0)
return map_idx;
map = env->used_maps[map_idx];
aux = &env->insn_aux_data[i];
aux->map_index = map_idx;
err = check_map_prog_compatibility(env, map, env->prog);
if (err)
return err;
if (insn[0].src_reg == BPF_PSEUDO_MAP_FD ||
insn[0].src_reg == BPF_PSEUDO_MAP_IDX) {
addr = (unsigned long)map;
@ -18978,13 +19029,11 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
if (off >= BPF_MAX_VAR_OFF) {
verbose(env, "direct value offset of %u is not allowed\n", off);
fdput(f);
return -EINVAL;
}
if (!map->ops->map_direct_value_addr) {
verbose(env, "no direct value access support for this map type\n");
fdput(f);
return -EINVAL;
}
@ -18992,7 +19041,6 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
if (err) {
verbose(env, "invalid access to map value pointer, value_size=%u off=%u\n",
map->value_size, off);
fdput(f);
return err;
}
@ -19003,70 +19051,39 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
insn[0].imm = (u32)addr;
insn[1].imm = addr >> 32;
/* check whether we recorded this map already */
for (j = 0; j < env->used_map_cnt; j++) {
if (env->used_maps[j] == map) {
aux->map_index = j;
fdput(f);
/* proceed with extra checks only if its newly added used map */
if (reused)
goto next_insn;
}
}
if (env->used_map_cnt >= MAX_USED_MAPS) {
verbose(env, "The total number of maps per program has reached the limit of %u\n",
MAX_USED_MAPS);
fdput(f);
return -E2BIG;
}
if (env->prog->sleepable)
atomic64_inc(&map->sleepable_refcnt);
/* hold the map. If the program is rejected by verifier,
* the map will be released by release_maps() or it
* will be used by the valid program until it's unloaded
* and all maps are released in bpf_free_used_maps()
*/
bpf_map_inc(map);
aux->map_index = env->used_map_cnt;
env->used_maps[env->used_map_cnt++] = map;
if (bpf_map_is_cgroup_storage(map) &&
bpf_cgroup_storage_assign(env->prog->aux, map)) {
verbose(env, "only one cgroup storage of each type is allowed\n");
fdput(f);
return -EBUSY;
}
if (map->map_type == BPF_MAP_TYPE_ARENA) {
if (env->prog->aux->arena) {
verbose(env, "Only one arena per program\n");
fdput(f);
return -EBUSY;
}
if (!env->allow_ptr_leaks || !env->bpf_capable) {
verbose(env, "CAP_BPF and CAP_PERFMON are required to use arena\n");
fdput(f);
return -EPERM;
}
if (!env->prog->jit_requested) {
verbose(env, "JIT is required to use arena\n");
fdput(f);
return -EOPNOTSUPP;
}
if (!bpf_jit_supports_arena()) {
verbose(env, "JIT doesn't support arena\n");
fdput(f);
return -EOPNOTSUPP;
}
env->prog->aux->arena = (void *)map;
if (!bpf_arena_get_user_vm_start(env->prog->aux->arena)) {
verbose(env, "arena's user address must be set via map_extra or mmap()\n");
fdput(f);
return -EINVAL;
}
}
fdput(f);
next_insn:
insn++;
i++;