bpf: charge user for creation of BPF maps and programs

since eBPF programs and maps use kernel memory consider it 'locked' memory
from user accounting point of view and charge it against RLIMIT_MEMLOCK limit.
This limit is typically set to 64Kbytes by distros, so almost all
bpf+tracing programs would need to increase it, since they use maps,
but kernel charges maximum map size upfront.
For example the hash map of 1024 elements will be charged as 64Kbyte.
It's inconvenient for current users and changes current behavior for root,
but probably worth doing to be consistent root vs non-root.

Similar accounting logic is done by mmap of perf_event.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 02fa3db3c1ec597b0b2d5ac8fc3907f06bcb6a4d..e3a51b74e275933700690afcc6c2c233b3612066 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -36,6 +36,8 @@ struct bpf_map {
        u32 key_size;
        u32 value_size;
        u32 max_entries;
+       u32 pages;
+       struct user_struct *user;
        const struct bpf_map_ops *ops;
        struct work_struct work;
 };
@@ -128,6 +130,7 @@ struct bpf_prog_aux {
        const struct bpf_verifier_ops *ops;
        struct bpf_map **used_maps;
        struct bpf_prog *prog;
+       struct user_struct *user;
        union {
                struct work_struct work;
                struct rcu_head rcu;

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b7b9501b41af4eab6a096601c3baf85c85854807..4817df5fffae86c1ccbcd385200c053e8eaad2ea 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -840,7 +840,7 @@ struct user_struct {
        struct hlist_node uidhash_node;
        kuid_t uid;
 
-#ifdef CONFIG_PERF_EVENTS
+#if defined(CONFIG_PERF_EVENTS) || defined(CONFIG_BPF_SYSCALL)
        atomic_long_t locked_vm;
 #endif
 };

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 2fecc4aed119fffa896a667fa2e295aeb370d874..f2d9e698c7538e61fa8dec26465608643770e06a 100644 (file)
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -49,7 +49,7 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
        array->map.key_size = attr->key_size;
        array->map.value_size = attr->value_size;
        array->map.max_entries = attr->max_entries;
-
+       array->map.pages = round_up(array_size, PAGE_SIZE) >> PAGE_SHIFT;
        array->elem_size = elem_size;
 
        return &array->map;

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 83c209d9b17ae6b23eb16d0fd0d94b873897ffba..28592d79502b0dcb0deac7dfb1ac10f07d435eb5 100644 (file)
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -88,6 +88,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
        htab->elem_size = sizeof(struct htab_elem) +
                          round_up(htab->map.key_size, 8) +
                          htab->map.value_size;
+
+       htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
+                                  htab->elem_size * htab->map.max_entries,
+                                  PAGE_SIZE) >> PAGE_SHIFT;
        return &htab->map;
 
 free_htab:

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 83697bc8e574aadafb3ab4db613a03c4f988f83e..f640e5f7afbd7cece735fcbc1fe34a6d0355337a 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -46,11 +46,38 @@ void bpf_register_map_type(struct bpf_map_type_list *tl)
        list_add(&tl->list_node, &bpf_map_types);
 }
 
+static int bpf_map_charge_memlock(struct bpf_map *map)
+{
+       struct user_struct *user = get_current_user();
+       unsigned long memlock_limit;
+
+       memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+
+       atomic_long_add(map->pages, &user->locked_vm);
+
+       if (atomic_long_read(&user->locked_vm) > memlock_limit) {
+               atomic_long_sub(map->pages, &user->locked_vm);
+               free_uid(user);
+               return -EPERM;
+       }
+       map->user = user;
+       return 0;
+}
+
+static void bpf_map_uncharge_memlock(struct bpf_map *map)
+{
+       struct user_struct *user = map->user;
+
+       atomic_long_sub(map->pages, &user->locked_vm);
+       free_uid(user);
+}
+
 /* called from workqueue */
 static void bpf_map_free_deferred(struct work_struct *work)
 {
        struct bpf_map *map = container_of(work, struct bpf_map, work);
 
+       bpf_map_uncharge_memlock(map);
        /* implementation dependent freeing */
        map->ops->map_free(map);
 }
@@ -110,6 +137,10 @@ static int map_create(union bpf_attr *attr)
 
        atomic_set(&map->refcnt, 1);
 
+       err = bpf_map_charge_memlock(map);
+       if (err)
+               goto free_map;
+
        err = anon_inode_getfd("bpf-map", &bpf_map_fops, map, O_RDWR | O_CLOEXEC);
 
        if (err < 0)
@@ -442,11 +473,37 @@ static void free_used_maps(struct bpf_prog_aux *aux)
        kfree(aux->used_maps);
 }
 
+static int bpf_prog_charge_memlock(struct bpf_prog *prog)
+{
+       struct user_struct *user = get_current_user();
+       unsigned long memlock_limit;
+
+       memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+
+       atomic_long_add(prog->pages, &user->locked_vm);
+       if (atomic_long_read(&user->locked_vm) > memlock_limit) {
+               atomic_long_sub(prog->pages, &user->locked_vm);
+               free_uid(user);
+               return -EPERM;
+       }
+       prog->aux->user = user;
+       return 0;
+}
+
+static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
+{
+       struct user_struct *user = prog->aux->user;
+
+       atomic_long_sub(prog->pages, &user->locked_vm);
+       free_uid(user);
+}
+
 static void __prog_put_rcu(struct rcu_head *rcu)
 {
        struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
 
        free_used_maps(aux);
+       bpf_prog_uncharge_memlock(aux->prog);
        bpf_prog_free(aux->prog);
 }
 
@@ -554,6 +611,10 @@ static int bpf_prog_load(union bpf_attr *attr)
        if (!prog)
                return -ENOMEM;
 
+       err = bpf_prog_charge_memlock(prog);
+       if (err)
+               goto free_prog_nouncharge;
+
        prog->len = attr->insn_cnt;
 
        err = -EFAULT;
@@ -595,6 +656,8 @@ static int bpf_prog_load(union bpf_attr *attr)
 free_used_maps:
        free_used_maps(prog->aux);
 free_prog:
+       bpf_prog_uncharge_memlock(prog);
+free_prog_nouncharge:
        bpf_prog_free(prog);
        return err;
 }