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bpf: map_get_next_key to return first key on NULL

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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>
This commit is contained in:
Teng Qin 2017-04-24 19:00:37 -07:00 committed by Greg Kroah-Hartman
parent 609124d603
commit ea7c24c785
3 changed files with 17 additions and 12 deletions
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2
kernel/bpf/arraymap.c
View File

@ -102,7 +102,7 @@ static void *array_map_lookup_elem(struct bpf_map *map, void *key)
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) {

9
kernel/bpf/hashtab.c
View File

@ -169,12 +169,15 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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 bpf_map *map, void *key, void *next_key)
/* 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)),

18
kernel/bpf/syscall.c
View File

@ -390,14 +390,18 @@ static int map_get_next_key(union bpf_attr *attr)
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);