[PATCH 18/39] bpf maps: switch to CLASS(fd, ...)

viro
2024-07-30T05:15:03Z

From: Al Viro <viro@zeniv.linux.org.uk>

Calling conventions for __bpf_map_get() would be more convenient
if it left fpdut() on failure to callers. Makes for simpler logics
in the callers.

Among other things, the proof of memory safety no longer has to
rely upon file->private_data never being ERR_PTR(...) for bpffs files.
Original calling conventions made it impossible for the caller to tell
whether __bpf_map_get() has returned ERR_PTR(-EINVAL) because it has found
the file not be a bpf map one (in which case it would've done fdput())
or because it found that ERR_PTR(-EINVAL) in file->private_data of a
bpf map file (in which case fdput() would _not_ have been done).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
include/linux/bpf.h | 9 +++-
kernel/bpf/map_in_map.c | 38 ++++---------
kernel/bpf/syscall.c | 117 ++++++++++++----------------------------
kernel/bpf/verifier.c | 19 +------
net/core/sock_map.c | 23 +++-----
5 files changed, 60 insertions(+), 146 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3b94ec161e8c..004d37e8b8df 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2227,7 +2227,14 @@ void __bpf_obj_drop_impl(void *p, const struct btf_record *rec, bool percpu);

struct bpf_map *bpf_map_get(u32 ufd);
struct bpf_map *bpf_map_get_with_uref(u32 ufd);
-struct bpf_map *__bpf_map_get(struct fd f);
+
+struct bpf_map *bpf_file_to_map(struct file *f);
+static inline struct bpf_map *__bpf_map_get(struct fd f)
+{
+ if (fd_empty(f))
+ return ERR_PTR(-EBADF);
+ return bpf_file_to_map(fd_file(f));
+}
void bpf_map_inc(struct bpf_map *map);
void bpf_map_inc_with_uref(struct bpf_map *map);
struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map, bool uref);
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index b4f18c85d7bc..645bd30bc9a9 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -11,24 +11,18 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
{
struct bpf_map *inner_map, *inner_map_meta;
u32 inner_map_meta_size;
- struct fd f;
- int ret;
+ CLASS(fd, f)(inner_map_ufd);

- f = fdget(inner_map_ufd);
inner_map = __bpf_map_get(f);
if (IS_ERR(inner_map))
return inner_map;

/* Does not support >1 level map-in-map */
- if (inner_map->inner_map_meta) {
- ret = -EINVAL;
- goto put;
- }
+ if (inner_map->inner_map_meta)
+ return ERR_PTR(-EINVAL);

- if (!inner_map->ops->map_meta_equal) {
- ret = -ENOTSUPP;
- goto put;
- }
+ if (!inner_map->ops->map_meta_equal)
+ return ERR_PTR(-ENOTSUPP);

inner_map_meta_size = sizeof(*inner_map_meta);
/* In some cases verifier needs to access beyond just base map. */
@@ -36,10 +30,8 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
inner_map_meta_size = sizeof(struct bpf_array);

inner_map_meta = kzalloc(inner_map_meta_size, GFP_USER);
- if (!inner_map_meta) {
- ret = -ENOMEM;
- goto put;
- }
+ if (!inner_map_meta)
+ return ERR_PTR(-ENOMEM);

inner_map_meta->map_type = inner_map->map_type;
inner_map_meta->key_size = inner_map->key_size;
@@ -53,8 +45,9 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
* invalid/empty/valid, but ERR_PTR in case of errors. During
* equality NULL or IS_ERR is equivalent.
*/
- ret = PTR_ERR(inner_map_meta->record);
- goto free;
+ struct bpf_map *ret = ERR_CAST(inner_map_meta->record);
+ kfree(inner_map_meta);
+ return ret;
}
/* Note: We must use the same BTF, as we also used btf_record_dup above
* which relies on BTF being same for both maps, as some members like
@@ -77,14 +70,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
inner_array_meta->elem_size = inner_array->elem_size;
inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;
}
-
- fdput(f);
return inner_map_meta;
-free:
- kfree(inner_map_meta);
-put:
- fdput(f);
- return ERR_PTR(ret);
}

void bpf_map_meta_free(struct bpf_map *map_meta)
@@ -110,9 +96,8 @@ void *bpf_map_fd_get_ptr(struct bpf_map *map,
int ufd)
{
struct bpf_map *inner_map, *inner_map_meta;
- struct fd f;
+ CLASS(fd, f)(ufd);

- f = fdget(ufd);
inner_map = __bpf_map_get(f);
if (IS_ERR(inner_map))
return inner_map;
@@ -123,7 +108,6 @@ void *bpf_map_fd_get_ptr(struct bpf_map *map,
else
inner_map = ERR_PTR(-EINVAL);

- fdput(f);
return inner_map;
}

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c5b252c0faa8..807042c643c8 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1418,19 +1418,11 @@ static int map_create(union bpf_attr *attr)
return err;
}

-/* if error is returned, fd is released.
- * On success caller should complete fd access with matching fdput()
- */
-struct bpf_map *__bpf_map_get(struct fd f)
+struct bpf_map *bpf_file_to_map(struct file *f)
{
- if (!fd_file(f))
- return ERR_PTR(-EBADF);
- if (fd_file(f)->f_op != &bpf_map_fops) {
- fdput(f);
+ if (unlikely(f->f_op != &bpf_map_fops))
return ERR_PTR(-EINVAL);
- }
-
- return fd_file(f)->private_data;
+ return f->private_data;
}

void bpf_map_inc(struct bpf_map *map)
@@ -1448,15 +1440,11 @@ EXPORT_SYMBOL_GPL(bpf_map_inc_with_uref);

struct bpf_map *bpf_map_get(u32 ufd)
{
- struct fd f = fdget(ufd);
- struct bpf_map *map;
-
- map = __bpf_map_get(f);
- if (IS_ERR(map))
- return map;
+ CLASS(fd, f)(ufd);
+ struct bpf_map *map = __bpf_map_get(f);

- bpf_map_inc(map);
- fdput(f);
+ if (!IS_ERR(map))
+ bpf_map_inc(map);

return map;
}
@@ -1464,15 +1452,11 @@ EXPORT_SYMBOL(bpf_map_get);

struct bpf_map *bpf_map_get_with_uref(u32 ufd)
{
- struct fd f = fdget(ufd);
- struct bpf_map *map;
-
- map = __bpf_map_get(f);
- if (IS_ERR(map))
- return map;
+ CLASS(fd, f)(ufd);
+ struct bpf_map *map = __bpf_map_get(f);

- bpf_map_inc_with_uref(map);
- fdput(f);
+ if (!IS_ERR(map))
+ bpf_map_inc_with_uref(map);

return map;
}
@@ -1537,11 +1521,9 @@ static int map_lookup_elem(union bpf_attr *attr)
{
void __user *ukey = u64_to_user_ptr(attr->key);
void __user *uvalue = u64_to_user_ptr(attr->value);
- int ufd = attr->map_fd;
struct bpf_map *map;
void *key, *value;
u32 value_size;
- struct fd f;
int err;

if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
@@ -1550,26 +1532,20 @@ static int map_lookup_elem(union bpf_attr *attr)
if (attr->flags & ~BPF_F_LOCK)
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
- if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
- err = -EPERM;
- goto err_put;
- }
+ if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
+ return -EPERM;

if ((attr->flags & BPF_F_LOCK) &&
- !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
- err = -EINVAL;
- goto err_put;
- }
+ !btf_record_has_field(map->record, BPF_SPIN_LOCK))
+ return -EINVAL;

key = __bpf_copy_key(ukey, map->key_size);
- if (IS_ERR(key)) {
- err = PTR_ERR(key);
- goto err_put;
- }
+ if (IS_ERR(key))
+ return PTR_ERR(key);

value_size = bpf_map_value_size(map);

@@ -1600,8 +1576,6 @@ static int map_lookup_elem(union bpf_attr *attr)
kvfree(value);
free_key:
kvfree(key);
-err_put:
- fdput(f);
return err;
}

@@ -1612,17 +1586,15 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
{
bpfptr_t ukey = make_bpfptr(attr->key, uattr.is_kernel);
bpfptr_t uvalue = make_bpfptr(attr->value, uattr.is_kernel);
- int ufd = attr->map_fd;
struct bpf_map *map;
void *key, *value;
u32 value_size;
- struct fd f;
int err;

if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
@@ -1660,7 +1632,6 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
kvfree(key);
err_put:
bpf_map_write_active_dec(map);
- fdput(f);
return err;
}

@@ -1669,16 +1640,14 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
static int map_delete_elem(union bpf_attr *attr, bpfptr_t uattr)
{
bpfptr_t ukey = make_bpfptr(attr->key, uattr.is_kernel);
- int ufd = attr->map_fd;
struct bpf_map *map;
- struct fd f;
void *key;
int err;

if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
@@ -1715,7 +1684,6 @@ static int map_delete_elem(union bpf_attr *attr, bpfptr_t uattr)
kvfree(key);
err_put:
bpf_map_write_active_dec(map);
- fdput(f);
return err;
}

@@ -1726,30 +1694,24 @@ static int map_get_next_key(union bpf_attr *attr)
{
void __user *ukey = u64_to_user_ptr(attr->key);
void __user *unext_key = u64_to_user_ptr(attr->next_key);
- int ufd = attr->map_fd;
struct bpf_map *map;
void *key, *next_key;
- struct fd f;
int err;

if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
- if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
- err = -EPERM;
- goto err_put;
- }
+ if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
+ return -EPERM;

if (ukey) {
key = __bpf_copy_key(ukey, map->key_size);
- if (IS_ERR(key)) {
- err = PTR_ERR(key);
- goto err_put;
- }
+ if (IS_ERR(key))
+ return PTR_ERR(key);
} else {
key = NULL;
}
@@ -1781,8 +1743,6 @@ static int map_get_next_key(union bpf_attr *attr)
kvfree(next_key);
free_key:
kvfree(key);
-err_put:
- fdput(f);
return err;
}

@@ -2011,11 +1971,9 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
{
void __user *ukey = u64_to_user_ptr(attr->key);
void __user *uvalue = u64_to_user_ptr(attr->value);
- int ufd = attr->map_fd;
struct bpf_map *map;
void *key, *value;
u32 value_size;
- struct fd f;
int err;

if (CHECK_ATTR(BPF_MAP_LOOKUP_AND_DELETE_ELEM))
@@ -2024,7 +1982,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
if (attr->flags & ~BPF_F_LOCK)
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
@@ -2094,7 +2052,6 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
kvfree(key);
err_put:
bpf_map_write_active_dec(map);
- fdput(f);
return err;
}

@@ -2102,27 +2059,22 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)

static int map_freeze(const union bpf_attr *attr)
{
- int err = 0, ufd = attr->map_fd;
+ int err = 0;
struct bpf_map *map;
- struct fd f;

if (CHECK_ATTR(BPF_MAP_FREEZE))
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->map_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);

- if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS || !IS_ERR_OR_NULL(map->record)) {
- fdput(f);
+ if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS || !IS_ERR_OR_NULL(map->record))
return -ENOTSUPP;
- }

- if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
- fdput(f);
+ if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE))
return -EPERM;
- }

mutex_lock(&map->freeze_mutex);
if (bpf_map_write_active(map)) {
@@ -2137,7 +2089,6 @@ static int map_freeze(const union bpf_attr *attr)
WRITE_ONCE(map->frozen, true);
err_put:
mutex_unlock(&map->freeze_mutex);
- fdput(f);
return err;
}

@@ -5178,14 +5129,13 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
cmd == BPF_MAP_LOOKUP_AND_DELETE_BATCH;
bool has_write = cmd != BPF_MAP_LOOKUP_BATCH;
struct bpf_map *map;
- int err, ufd;
- struct fd f;
+ int err;

if (CHECK_ATTR(BPF_MAP_BATCH))
return -EINVAL;

- ufd = attr->batch.map_fd;
- f = fdget(ufd);
+ CLASS(fd, f)(attr->batch.map_fd);
+
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
@@ -5213,7 +5163,6 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
maybe_wait_bpf_programs(map);
bpf_map_write_active_dec(map);
}
- fdput(f);
return err;
}

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d54f61e12062..011c51a84158 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18419,7 +18419,6 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
struct bpf_insn_aux_data *aux)
{
struct bpf_map *map;
- struct fd f;
u64 addr;
u32 fd;
int err;
@@ -18470,7 +18469,7 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
break;
}

- f = fdget(fd);
+ CLASS(fd, f)(fd);
map = __bpf_map_get(f);
if (IS_ERR(map)) {
verbose(env, "fd %d is not pointing to valid bpf_map\n", fd);
@@ -18478,10 +18477,8 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
}

err = check_map_prog_compatibility(env, map, env->prog);
- if (err) {
- fdput(f);
+ if (err)
return err;
- }

if (insn[0].src_reg == BPF_PSEUDO_MAP_FD ||
insn[0].src_reg == BPF_PSEUDO_MAP_IDX) {
@@ -18491,13 +18488,11 @@ static int do_one_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;
}

@@ -18505,7 +18500,6 @@ static int do_one_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;
}

@@ -18520,7 +18514,6 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
for (int i = 0; i < env->used_map_cnt; i++) {
if (env->used_maps[i] == map) {
aux->map_index = i;
- fdput(f);
return 0;
}
}
@@ -18528,7 +18521,6 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
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;
}

@@ -18547,39 +18539,32 @@ static int do_one_ldimm64(struct bpf_verifier_env *env,
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);
return 0;
}

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index d3dbb92153f2..0f5f80f44d52 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -67,46 +67,39 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr)

int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog)
{
- u32 ufd = attr->target_fd;
struct bpf_map *map;
- struct fd f;
int ret;

if (attr->attach_flags || attr->replace_bpf_fd)
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->target_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
mutex_lock(&sockmap_mutex);
ret = sock_map_prog_update(map, prog, NULL, NULL, attr->attach_type);
mutex_unlock(&sockmap_mutex);
- fdput(f);
return ret;
}

int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
{
- u32 ufd = attr->target_fd;
struct bpf_prog *prog;
struct bpf_map *map;
- struct fd f;
int ret;

if (attr->attach_flags || attr->replace_bpf_fd)
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->target_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);

prog = bpf_prog_get(attr->attach_bpf_fd);
- if (IS_ERR(prog)) {
- ret = PTR_ERR(prog);
- goto put_map;
- }
+ if (IS_ERR(prog))
+ return PTR_ERR(prog);

if (prog->type != ptype) {
ret = -EINVAL;
@@ -118,8 +111,6 @@ int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
mutex_unlock(&sockmap_mutex);
put_prog:
bpf_prog_put(prog);
-put_map:
- fdput(f);
return ret;
}

@@ -1550,18 +1541,17 @@ int sock_map_bpf_prog_query(const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
- u32 prog_cnt = 0, flags = 0, ufd = attr->target_fd;
+ u32 prog_cnt = 0, flags = 0;
struct bpf_prog **pprog;
struct bpf_prog *prog;
struct bpf_map *map;
- struct fd f;
u32 id = 0;
int ret;

if (attr->query.query_flags)
return -EINVAL;

- f = fdget(ufd);
+ CLASS(fd, f)(attr->target_fd);
map = __bpf_map_get(f);
if (IS_ERR(map))
return PTR_ERR(map);
@@ -1593,7 +1583,6 @@ int sock_map_bpf_prog_query(const union bpf_attr *attr,
copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
ret = -EFAULT;

- fdput(f);
return ret;
}

--
2.39.2