[PATCH 5.7 127/265] devmap: Use bpf_map_area_alloc() for allocating hash buckets

Sasha Levin
2020-06-29T22:05:40Z

From: Toke Høiland-Jørgensen <toke@redhat.com>

[ Upstream commit 99c51064fb06146b3d494b745c947e438a10aaa7 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/devmap.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 58bdca5d978a8..badf382bbd365 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -85,12 +85,13 @@ 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]);
@@ -138,7 +139,8 @@ 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;

@@ -223,7 +225,7 @@ 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;
--
2.25.1