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>

1 files changed, 63 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 83697bc8e574..f640e5f7afbd 100644
--- 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;
 }