bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall

The previous patch implemented a bpf queue/stack maps that
provided the peek/pop/push functions.  There is not a direct
relationship between those functions and the current maps
syscalls, hence a new MAP_LOOKUP_AND_DELETE_ELEM syscall is added,
this is mapped to the pop operation in the queue/stack maps
and it is still to implement in other kind of maps.

Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 1617407f9ee5..49ae64a26562 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -999,6 +999,69 @@ err_put:
         return err;
 }
 
+#define BPF_MAP_LOOKUP_AND_DELETE_ELEM_LAST_FIELD value
+
+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, *ptr;
+        u32 value_size;
+        struct fd f;
+        int err;
+
+        if (CHECK_ATTR(BPF_MAP_LOOKUP_AND_DELETE_ELEM))
+                return -EINVAL;
+
+        f = fdget(ufd);
+        map = __bpf_map_get(f);
+        if (IS_ERR(map))
+                return PTR_ERR(map);
+
+        if (!(f.file->f_mode & FMODE_CAN_WRITE)) {
+                err = -EPERM;
+                goto err_put;
+        }
+
+        key = __bpf_copy_key(ukey, map->key_size);
+        if (IS_ERR(key)) {
+                err = PTR_ERR(key);
+                goto err_put;
+        }
+
+        value_size = map->value_size;
+
+        err = -ENOMEM;
+        value = kmalloc(value_size, GFP_USER | __GFP_NOWARN);
+        if (!value)
+                goto free_key;
+
+        if (map->map_type == BPF_MAP_TYPE_QUEUE ||
+            map->map_type == BPF_MAP_TYPE_STACK) {
+                err = map->ops->map_pop_elem(map, value);
+        } else {
+                err = -ENOTSUPP;
+        }
+
+        if (err)
+                goto free_value;
+
+        if (copy_to_user(uvalue, value, value_size) != 0)
+                goto free_value;
+
+        err = 0;
+
+free_value:
+        kfree(value);
+free_key:
+        kfree(key);
+err_put:
+        fdput(f);
+        return err;
+}
+
 static const struct bpf_prog_ops * const bpf_prog_types[] = {
 #define BPF_PROG_TYPE(_id, _name) \
         [_id] = & _name ## _prog_ops,
@@ -2472,6 +2535,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
         case BPF_TASK_FD_QUERY:
                 err = bpf_task_fd_query(&attr, uattr);
                 break;
+        case BPF_MAP_LOOKUP_AND_DELETE_ELEM:
+                err = map_lookup_and_delete_elem(&attr);
+                break;
         default:
                 err = -EINVAL;
                 break;