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Message-Id: <20210611042442.65444-3-alexei.starovoitov@gmail.com>
Date: Thu, 10 Jun 2021 21:24:41 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: davem@...emloft.net
Cc: daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org,
bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH v2 bpf-next 2/3] bpf: Add verifier checks for bpf_timer.
From: Alexei Starovoitov <ast@...nel.org>
Add appropriate safety checks for bpf_timer:
- restrict to array, hash, lru. per-cpu maps cannot be supported.
- kfree bpf_timer during map_delete_elem and map_free.
- verifier btf checks.
- safe interaction with lookup/update/delete operations and iterator.
- relax the first field only requirement of the previous patch.
- search for bpf_timer in datasec in case it was placed in global data.
- check prog_rdonly, frozen flags.
- mmap is not allowed.
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
include/linux/bpf.h | 45 ++++++++++++++++------
include/linux/btf.h | 1 +
kernel/bpf/arraymap.c | 14 +++++++
kernel/bpf/btf.c | 77 +++++++++++++++++++++++++++++++-------
kernel/bpf/hashtab.c | 56 +++++++++++++++++++++------
kernel/bpf/helpers.c | 2 +-
kernel/bpf/local_storage.c | 4 +-
kernel/bpf/map_in_map.c | 1 +
kernel/bpf/syscall.c | 21 +++++++++--
kernel/bpf/verifier.c | 30 +++++++++++++--
10 files changed, 205 insertions(+), 46 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3816b6bae6d3..7c403235c7e8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -168,6 +168,7 @@ struct bpf_map {
u32 max_entries;
u32 map_flags;
int spin_lock_off; /* >=0 valid offset, <0 error */
+ int timer_off; /* >=0 valid offset, <0 error */
u32 id;
int numa_node;
u32 btf_key_type_id;
@@ -197,24 +198,46 @@ static inline bool map_value_has_spin_lock(const struct bpf_map *map)
return map->spin_lock_off >= 0;
}
-static inline void check_and_init_map_lock(struct bpf_map *map, void *dst)
+static inline bool map_value_has_timer(const struct bpf_map *map)
{
- if (likely(!map_value_has_spin_lock(map)))
- return;
- *(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
- (struct bpf_spin_lock){};
+ return map->timer_off >= 0;
}
-/* copy everything but bpf_spin_lock */
+static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
+{
+ if (unlikely(map_value_has_spin_lock(map)))
+ *(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
+ (struct bpf_spin_lock){};
+ if (unlikely(map_value_has_timer(map)))
+ *(struct bpf_timer *)(dst + map->timer_off) =
+ (struct bpf_timer){};
+}
+
+/* copy everything but bpf_spin_lock and bpf_timer. There could be one of each. */
static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
{
+ u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0;
+
if (unlikely(map_value_has_spin_lock(map))) {
- u32 off = map->spin_lock_off;
+ s_off = map->spin_lock_off;
+ s_sz = sizeof(struct bpf_spin_lock);
+ } else if (unlikely(map_value_has_timer(map))) {
+ t_off = map->timer_off;
+ t_sz = sizeof(struct bpf_timer);
+ }
- memcpy(dst, src, off);
- memcpy(dst + off + sizeof(struct bpf_spin_lock),
- src + off + sizeof(struct bpf_spin_lock),
- map->value_size - off - sizeof(struct bpf_spin_lock));
+ if (unlikely(s_sz || t_sz)) {
+ if (s_off < t_off || !s_sz) {
+ swap(s_off, t_off);
+ swap(s_sz, t_sz);
+ }
+ memcpy(dst, src, t_off);
+ memcpy(dst + t_off + t_sz,
+ src + t_off + t_sz,
+ s_off - t_off - t_sz);
+ memcpy(dst + s_off + s_sz,
+ src + s_off + s_sz,
+ map->value_size - s_off - s_sz);
} else {
memcpy(dst, src, map->value_size);
}
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 94a0c976c90f..214fde93214b 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -99,6 +99,7 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
const struct btf_member *m,
u32 expected_offset, u32 expected_size);
int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
+int btf_find_timer(const struct btf *btf, const struct btf_type *t);
bool btf_type_is_void(const struct btf_type *t);
s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 3c4105603f9d..5c84ab7f8872 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -287,6 +287,12 @@ static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key
return 0;
}
+static void check_and_free_timer_in_array(struct bpf_array *arr, void *val)
+{
+ if (unlikely(map_value_has_timer(&arr->map)))
+ bpf_timer_cancel_and_free(val + arr->map.timer_off);
+}
+
/* Called from syscall or from eBPF program */
static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
@@ -321,6 +327,7 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
copy_map_value_locked(map, val, value, false);
else
copy_map_value(map, val, value);
+ check_and_free_timer_in_array(array, val);
}
return 0;
}
@@ -378,10 +385,17 @@ static void *array_map_vmalloc_addr(struct bpf_array *array)
static void array_map_free(struct bpf_map *map)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
+ int i;
if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
bpf_array_free_percpu(array);
+ if (unlikely(map_value_has_timer(map)))
+ for (i = 0; i < array->map.max_entries; i++)
+ bpf_timer_cancel_and_free(array->value +
+ array->elem_size * i +
+ map->timer_off);
+
if (array->map.map_flags & BPF_F_MMAPABLE)
bpf_map_area_free(array_map_vmalloc_addr(array));
else
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index a6e39c5ea0bf..28a8014b8379 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3046,43 +3046,92 @@ static void btf_struct_log(struct btf_verifier_env *env,
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}
-/* find 'struct bpf_spin_lock' in map value.
- * return >= 0 offset if found
- * and < 0 in case of error
- */
-int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
+static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t,
+ const char *name, int sz, int align)
{
const struct btf_member *member;
u32 i, off = -ENOENT;
- if (!__btf_type_is_struct(t))
- return -EINVAL;
-
for_each_member(i, t, member) {
const struct btf_type *member_type = btf_type_by_id(btf,
member->type);
if (!__btf_type_is_struct(member_type))
continue;
- if (member_type->size != sizeof(struct bpf_spin_lock))
+ if (member_type->size != sz)
continue;
- if (strcmp(__btf_name_by_offset(btf, member_type->name_off),
- "bpf_spin_lock"))
+ if (strcmp(__btf_name_by_offset(btf, member_type->name_off), name))
continue;
if (off != -ENOENT)
- /* only one 'struct bpf_spin_lock' is allowed */
+ /* only one such field is allowed */
return -E2BIG;
off = btf_member_bit_offset(t, member);
if (off % 8)
/* valid C code cannot generate such BTF */
return -EINVAL;
off /= 8;
- if (off % __alignof__(struct bpf_spin_lock))
- /* valid struct bpf_spin_lock will be 4 byte aligned */
+ if (off % align)
+ return -EINVAL;
+ }
+ return off;
+}
+
+static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
+ const char *name, int sz, int align)
+{
+ const struct btf_var_secinfo *vsi;
+ u32 i, off = -ENOENT;
+
+ for_each_vsi(i, t, vsi) {
+ const struct btf_type *var = btf_type_by_id(btf, vsi->type);
+ const struct btf_type *var_type = btf_type_by_id(btf, var->type);
+
+ if (!__btf_type_is_struct(var_type))
+ continue;
+ if (var_type->size != sz)
+ continue;
+ if (vsi->size != sz)
+ continue;
+ if (strcmp(__btf_name_by_offset(btf, var_type->name_off), name))
+ continue;
+ if (off != -ENOENT)
+ /* only one such field is allowed */
+ return -E2BIG;
+ off = vsi->offset;
+ if (off % align)
return -EINVAL;
}
return off;
}
+static int btf_find_field(const struct btf *btf, const struct btf_type *t,
+ const char *name, int sz, int align)
+{
+
+ if (__btf_type_is_struct(t))
+ return btf_find_struct_field(btf, t, name, sz, align);
+ else if (btf_type_is_datasec(t))
+ return btf_find_datasec_var(btf, t, name, sz, align);
+ return -EINVAL;
+}
+
+/* find 'struct bpf_spin_lock' in map value.
+ * return >= 0 offset if found
+ * and < 0 in case of error
+ */
+int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
+{
+ return btf_find_field(btf, t, "bpf_spin_lock",
+ sizeof(struct bpf_spin_lock),
+ __alignof__(struct bpf_spin_lock));
+}
+
+int btf_find_timer(const struct btf *btf, const struct btf_type *t)
+{
+ return btf_find_field(btf, t, "bpf_timer",
+ sizeof(struct bpf_timer),
+ __alignof__(struct bpf_timer));
+}
+
static void __btf_struct_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct btf_show *show)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 6f6681b07364..c885492d0a76 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -244,6 +244,17 @@ static void htab_free_elems(struct bpf_htab *htab)
cond_resched();
}
free_elems:
+ if (unlikely(map_value_has_timer(&htab->map)))
+ for (i = 0; i < htab->map.max_entries; i++) {
+ struct htab_elem *elem;
+
+ elem = get_htab_elem(htab, i);
+ bpf_timer_cancel_and_free(elem->key +
+ round_up(htab->map.key_size, 8) +
+ htab->map.timer_off);
+ cond_resched();
+ }
+
bpf_map_area_free(htab->elems);
}
@@ -265,8 +276,11 @@ static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
struct htab_elem *l;
if (node) {
+ u32 key_size = htab->map.key_size;
l = container_of(node, struct htab_elem, lru_node);
- memcpy(l->key, key, htab->map.key_size);
+ memcpy(l->key, key, key_size);
+ check_and_init_map_value(&htab->map,
+ l->key + round_up(key_size, 8));
return l;
}
@@ -694,6 +708,14 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map,
return insn - insn_buf;
}
+static void check_and_free_timer(struct bpf_htab *htab, struct htab_elem *elem)
+{
+ if (unlikely(map_value_has_timer(&htab->map)))
+ bpf_timer_cancel_and_free(elem->key +
+ round_up(htab->map.key_size, 8) +
+ htab->map.timer_off);
+}
+
/* It is called from the bpf_lru_list when the LRU needs to delete
* older elements from the htab.
*/
@@ -718,6 +740,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
if (l == tgt_l) {
hlist_nulls_del_rcu(&l->hash_node);
+ check_and_free_timer(htab, l);
break;
}
@@ -789,6 +812,7 @@ static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
{
if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
+ check_and_free_timer(htab, l);
kfree(l);
}
@@ -816,6 +840,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
htab_put_fd_value(htab, l);
if (htab_is_prealloc(htab)) {
+ check_and_free_timer(htab, l);
__pcpu_freelist_push(&htab->freelist, &l->fnode);
} else {
atomic_dec(&htab->count);
@@ -919,8 +944,8 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
l_new = ERR_PTR(-ENOMEM);
goto dec_count;
}
- check_and_init_map_lock(&htab->map,
- l_new->key + round_up(key_size, 8));
+ check_and_init_map_value(&htab->map,
+ l_new->key + round_up(key_size, 8));
}
memcpy(l_new->key, key, key_size);
@@ -1060,6 +1085,8 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
hlist_nulls_del_rcu(&l_old->hash_node);
if (!htab_is_prealloc(htab))
free_htab_elem(htab, l_old);
+ else
+ check_and_free_timer(htab, l_old);
}
ret = 0;
err:
@@ -1067,6 +1094,12 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
return ret;
}
+static void htab_lru_push_free(struct bpf_htab *htab, struct htab_elem *elem)
+{
+ check_and_free_timer(htab, elem);
+ bpf_lru_push_free(&htab->lru, &elem->lru_node);
+}
+
static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
@@ -1099,7 +1132,8 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
l_new = prealloc_lru_pop(htab, key, hash);
if (!l_new)
return -ENOMEM;
- memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
+ copy_map_value(&htab->map,
+ l_new->key + round_up(map->key_size, 8), value);
ret = htab_lock_bucket(htab, b, hash, &flags);
if (ret)
@@ -1125,9 +1159,9 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
htab_unlock_bucket(htab, b, hash, flags);
if (ret)
- bpf_lru_push_free(&htab->lru, &l_new->lru_node);
+ htab_lru_push_free(htab, l_new);
else if (l_old)
- bpf_lru_push_free(&htab->lru, &l_old->lru_node);
+ htab_lru_push_free(htab, l_old);
return ret;
}
@@ -1332,7 +1366,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
htab_unlock_bucket(htab, b, hash, flags);
if (l)
- bpf_lru_push_free(&htab->lru, &l->lru_node);
+ htab_lru_push_free(htab, l);
return ret;
}
@@ -1449,7 +1483,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
else
copy_map_value(map, value, l->key +
roundup_key_size);
- check_and_init_map_lock(map, value);
+ check_and_init_map_value(map, value);
}
hlist_nulls_del_rcu(&l->hash_node);
@@ -1460,7 +1494,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
htab_unlock_bucket(htab, b, hash, bflags);
if (is_lru_map && l)
- bpf_lru_push_free(&htab->lru, &l->lru_node);
+ htab_lru_push_free(htab, l);
return ret;
}
@@ -1638,7 +1672,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
true);
else
copy_map_value(map, dst_val, value);
- check_and_init_map_lock(map, dst_val);
+ check_and_init_map_value(map, dst_val);
}
if (do_delete) {
hlist_nulls_del_rcu(&l->hash_node);
@@ -1665,7 +1699,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
while (node_to_free) {
l = node_to_free;
node_to_free = node_to_free->batch_flink;
- bpf_lru_push_free(&htab->lru, &l->lru_node);
+ htab_lru_push_free(htab, l);
}
next_batch:
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 3a693d451ca3..b8df592c33cc 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1072,7 +1072,7 @@ BPF_CALL_5(bpf_timer_init, struct bpf_timer_kern *, timer, void *, cb, int, flag
goto out;
}
t->callback_fn = cb;
- t->value = (void *)timer /* - offset of bpf_timer inside elem */;
+ t->value = (void *)timer - map->timer_off;
t->map = map;
t->prog = prog;
hrtimer_init(&t->timer, clockid, HRTIMER_MODE_REL_SOFT);
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index bd11db9774c3..95d70a08325d 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -173,7 +173,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *key,
return -ENOMEM;
memcpy(&new->data[0], value, map->value_size);
- check_and_init_map_lock(map, new->data);
+ check_and_init_map_value(map, new->data);
new = xchg(&storage->buf, new);
kfree_rcu(new, rcu);
@@ -509,7 +509,7 @@ struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
map->numa_node);
if (!storage->buf)
goto enomem;
- check_and_init_map_lock(map, storage->buf->data);
+ check_and_init_map_value(map, storage->buf->data);
} else {
storage->percpu_buf = bpf_map_alloc_percpu(map, size, 8, gfp);
if (!storage->percpu_buf)
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 39ab0b68cade..2f961b941159 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -50,6 +50,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
inner_map_meta->map_flags = inner_map->map_flags;
inner_map_meta->max_entries = inner_map->max_entries;
inner_map_meta->spin_lock_off = inner_map->spin_lock_off;
+ inner_map_meta->timer_off = inner_map->timer_off;
/* Misc members not needed in bpf_map_meta_equal() check. */
inner_map_meta->ops = inner_map->ops;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 50457019da27..0e53f9e10e1a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -259,8 +259,8 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
copy_map_value_locked(map, value, ptr, true);
else
copy_map_value(map, value, ptr);
- /* mask lock, since value wasn't zero inited */
- check_and_init_map_lock(map, value);
+ /* mask lock and timer, since value wasn't zero inited */
+ check_and_init_map_value(map, value);
}
rcu_read_unlock();
}
@@ -622,7 +622,8 @@ static int bpf_map_mmap(struct file *filp, struct vm_area_struct *vma)
struct bpf_map *map = filp->private_data;
int err;
- if (!map->ops->map_mmap || map_value_has_spin_lock(map))
+ if (!map->ops->map_mmap || map_value_has_spin_lock(map) ||
+ map_value_has_timer(map))
return -ENOTSUPP;
if (!(vma->vm_flags & VM_SHARED))
@@ -792,6 +793,16 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
}
}
+ map->timer_off = btf_find_timer(btf, value_type);
+ if (map_value_has_timer(map)) {
+ if (map->map_flags & BPF_F_RDONLY_PROG)
+ return -EACCES;
+ if (map->map_type != BPF_MAP_TYPE_HASH &&
+ map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+ map->map_type != BPF_MAP_TYPE_ARRAY)
+ return -ENOTSUPP;
+ }
+
if (map->ops->map_check_btf)
ret = map->ops->map_check_btf(map, btf, key_type, value_type);
@@ -843,6 +854,7 @@ static int map_create(union bpf_attr *attr)
mutex_init(&map->freeze_mutex);
map->spin_lock_off = -EINVAL;
+ map->timer_off = -EINVAL;
if (attr->btf_key_type_id || attr->btf_value_type_id ||
/* Even the map's value is a kernel's struct,
* the bpf_prog.o must have BTF to begin with
@@ -1590,7 +1602,8 @@ static int map_freeze(const union bpf_attr *attr)
if (IS_ERR(map))
return PTR_ERR(map);
- if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
+ if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS ||
+ map_value_has_timer(map)) {
fdput(f);
return -ENOTSUPP;
}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 44ec9760b562..0ddafa91d0d3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3241,6 +3241,15 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
return -EACCES;
}
}
+ if (map_value_has_timer(map)) {
+ u32 t = map->timer_off;
+
+ if (reg->smin_value + off < t + sizeof(struct bpf_timer) &&
+ t < reg->umax_value + off + size) {
+ verbose(env, "bpf_timer cannot be accessed directly by load/store\n");
+ return -EACCES;
+ }
+ }
return err;
}
@@ -4675,9 +4684,24 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,
map->name);
return -EINVAL;
}
- if (val) {
- /* This restriction will be removed in the next patch */
- verbose(env, "bpf_timer field can only be first in the map value element\n");
+ if (!map_value_has_timer(map)) {
+ if (map->timer_off == -E2BIG)
+ verbose(env,
+ "map '%s' has more than one 'struct bpf_timer'\n",
+ map->name);
+ else if (map->timer_off == -ENOENT)
+ verbose(env,
+ "map '%s' doesn't have 'struct bpf_timer'\n",
+ map->name);
+ else
+ verbose(env,
+ "map '%s' is not a struct type or bpf_timer is mangled\n",
+ map->name);
+ return -EINVAL;
+ }
+ if (map->timer_off != val + reg->off) {
+ verbose(env, "off %lld doesn't point to 'struct bpf_timer' that is at %d\n",
+ val + reg->off, map->timer_off);
return -EINVAL;
}
WARN_ON(meta->map_ptr);
--
2.30.2
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