4.4-stable review patch. If anyone has any objections, please let me know.
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From: Teng Qin qinteng@fb.com
commit 8fe45924387be6b5c1be59a7eb330790c61d5d10 upstream.
When iterating through a map, we need to find a key that does not exist in the map so map_get_next_key will give us the first key of the map. This often requires a lot of guessing in production systems.
This patch makes map_get_next_key return the first key when the key pointer in the parameter is NULL.
Signed-off-by: Teng Qin qinteng@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Chenbo Feng fengc@google.com Cc: Lorenzo Colitti lorenzo@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/bpf/arraymap.c | 2 +- kernel/bpf/hashtab.c | 9 +++++---- kernel/bpf/syscall.c | 18 +++++++++++------- 3 files changed, 17 insertions(+), 12 deletions(-)
--- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -102,7 +102,7 @@ static void *array_map_lookup_elem(struc static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key) { struct bpf_array *array = container_of(map, struct bpf_array, map); - u32 index = *(u32 *)key; + u32 index = key ? *(u32 *)key : U32_MAX; u32 *next = (u32 *)next_key;
if (index >= array->map.max_entries) { --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -169,12 +169,15 @@ static int htab_map_get_next_key(struct struct hlist_head *head; struct htab_elem *l, *next_l; u32 hash, key_size; - int i; + int i = 0;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
+ if (!key) + goto find_first_elem; + hash = htab_map_hash(key, key_size);
head = select_bucket(htab, hash); @@ -182,10 +185,8 @@ static int htab_map_get_next_key(struct /* lookup the key */ l = lookup_elem_raw(head, hash, key, key_size);
- if (!l) { - i = 0; + if (!l) goto find_first_elem; - }
/* key was found, get next key in the same bucket */ next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)), --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -390,14 +390,18 @@ static int map_get_next_key(union bpf_at if (IS_ERR(map)) return PTR_ERR(map);
- err = -ENOMEM; - key = kmalloc(map->key_size, GFP_USER); - if (!key) - goto err_put; + if (ukey) { + err = -ENOMEM; + key = kmalloc(map->key_size, GFP_USER); + if (!key) + goto err_put;
- err = -EFAULT; - if (copy_from_user(key, ukey, map->key_size) != 0) - goto free_key; + err = -EFAULT; + if (copy_from_user(key, ukey, map->key_size) != 0) + goto free_key; + } else { + key = NULL; + }
err = -ENOMEM; next_key = kmalloc(map->key_size, GFP_USER);