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Commit fcbc8d0e authored by Teng Qin's avatar Teng Qin Committed by Greg Kroah-Hartman
Browse files

bpf: map_get_next_key to return first key on NULL 



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: default avatarTeng Qin <qinteng@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarChenbo Feng <fengc@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8f54ead2

kernel/bpf/arraymap.c

+1 −1
Original line number Diff line number Diff line
@@ -190,7 +190,7 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value) 
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) {

kernel/bpf/hashtab.c

+5 −4
Original line number Diff line number Diff line
@@ -326,12 +326,15 @@ 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);
@@ -339,10 +342,8 @@ 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)),

kernel/bpf/syscall.c

+12 −8
Original line number Diff line number Diff line
@@ -508,6 +508,7 @@ static int map_get_next_key(union bpf_attr *attr) 
	if (IS_ERR(map))

		return PTR_ERR(map);



	if (ukey) {

		err = -ENOMEM;

		key = kmalloc(map->key_size, GFP_USER);

		if (!key)
@@ -516,6 +517,9 @@ static int map_get_next_key(union bpf_attr *attr) 
		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);