1 files changed, 39 insertions, 3 deletions

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 6d3b22c5ad68..937776531998 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -804,11 +804,11 @@ dec_count:
 static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
 		       u64 map_flags)
 {
-	if (l_old && map_flags == BPF_NOEXIST)
+	if (l_old && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
 		/* elem already exists */
 		return -EEXIST;
 
-	if (!l_old && map_flags == BPF_EXIST)
+	if (!l_old && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
 		/* elem doesn't exist, cannot update it */
 		return -ENOENT;
 
@@ -827,7 +827,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	u32 key_size, hash;
 	int ret;
 
-	if (unlikely(map_flags > BPF_EXIST))
+	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST))
 		/* unknown flags */
 		return -EINVAL;
 
@@ -840,6 +840,28 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	b = __select_bucket(htab, hash);
 	head = &b->head;
 
+	if (unlikely(map_flags & BPF_F_LOCK)) {
+		if (unlikely(!map_value_has_spin_lock(map)))
+			return -EINVAL;
+		/* find an element without taking the bucket lock */
+		l_old = lookup_nulls_elem_raw(head, hash, key, key_size,
+					      htab->n_buckets);
+		ret = check_flags(htab, l_old, map_flags);
+		if (ret)
+			return ret;
+		if (l_old) {
+			/* grab the element lock and update value in place */
+			copy_map_value_locked(map,
+					      l_old->key + round_up(key_size, 8),
+					      value, false);
+			return 0;
+		}
+		/* fall through, grab the bucket lock and lookup again.
+		 * 99.9% chance that the element won't be found,
+		 * but second lookup under lock has to be done.
+		 */
+	}
+
 	/* bpf_map_update_elem() can be called in_irq() */
 	raw_spin_lock_irqsave(&b->lock, flags);
 
@@ -849,6 +871,20 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	if (ret)
 		goto err;
 
+	if (unlikely(l_old && (map_flags & BPF_F_LOCK))) {
+		/* first lookup without the bucket lock didn't find the element,
+		 * but second lookup with the bucket lock found it.
+		 * This case is highly unlikely, but has to be dealt with:
+		 * grab the element lock in addition to the bucket lock
+		 * and update element in place
+		 */
+		copy_map_value_locked(map,
+				      l_old->key + round_up(key_size, 8),
+				      value, false);
+		ret = 0;
+		goto err;
+	}
+
 	l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
 				l_old);
 	if (IS_ERR(l_new)) {