devmap: Use bpf_map_area_alloc() for allocating hash buckets

Syzkaller discovered that creating a hash of type devmap_hash with a large
number of entries can hit the memory allocator limit for allocating
contiguous memory regions. There's really no reason to use kmalloc_array()
directly in the devmap code, so just switch it to the existing
bpf_map_area_alloc() function that is used elsewhere.

Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200616142829.114173-1-toke@redhat.com

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 0cbb72c..5fdbc77 100644 (file)
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -86,12 +86,13 @@ static DEFINE_PER_CPU(struct list_head, dev_flush_list);
 static DEFINE_SPINLOCK(dev_map_lock);
 static LIST_HEAD(dev_map_list);
 
-static struct hlist_head *dev_map_create_hash(unsigned int entries)
+static struct hlist_head *dev_map_create_hash(unsigned int entries,
+                                             int numa_node)
 {
        int i;
        struct hlist_head *hash;
 
-       hash = kmalloc_array(entries, sizeof(*hash), GFP_KERNEL);
+       hash = bpf_map_area_alloc(entries * sizeof(*hash), numa_node);
        if (hash != NULL)
                for (i = 0; i < entries; i++)
                        INIT_HLIST_HEAD(&hash[i]);
@@ -145,7 +146,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
                return -EINVAL;
 
        if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
-               dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets);
+               dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets,
+                                                          dtab->map.numa_node);
                if (!dtab->dev_index_head)
                        goto free_charge;
 
@@ -232,7 +234,7 @@ static void dev_map_free(struct bpf_map *map)
                        }
                }
 
-               kfree(dtab->dev_index_head);
+               bpf_map_area_free(dtab->dev_index_head);
        } else {
                for (i = 0; i < dtab->map.max_entries; i++) {
                        struct bpf_dtab_netdev *dev;