Commit c1cdf65d authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Daniel Borkmann
Browse files

bpf, sockmap: Return socket cookie on lookup from syscall 



Tooling that populates the SOCK{MAP,HASH} with sockets from user-space
needs a way to inspect its contents. Returning the struct sock * that the
map holds to user-space is neither safe nor useful. An approach established
by REUSEPORT_SOCKARRAY is to return a socket cookie (a unique identifier)
instead.

Since socket cookies are u64 values, SOCK{MAP,HASH} need to support such a
value size for lookup to be possible. This requires special handling on
update, though. Attempts to do a lookup on a map holding u32 values will be
met with ENOSPC error.

Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200218171023.844439-7-jakub@cloudflare.com
parent 6e830c2f

net/core/sock_map.c

+53 −4
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/skmsg.h>

#include <linux/list.h>

#include <linux/jhash.h>

#include <linux/sock_diag.h>



struct bpf_stab {

	struct bpf_map map;
@@ -31,7 +32,8 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr) 
		return ERR_PTR(-EPERM);

	if (attr->max_entries == 0 ||

	    attr->key_size    != 4 ||

	    attr->value_size  != 4 ||

	    (attr->value_size != sizeof(u32) &&

	     attr->value_size != sizeof(u64)) ||

	    attr->map_flags & ~SOCK_CREATE_FLAG_MASK)

		return ERR_PTR(-EINVAL);
@@ -302,6 +304,21 @@ static void *sock_map_lookup(struct bpf_map *map, void *key) 
	return ERR_PTR(-EOPNOTSUPP);

}



static void *sock_map_lookup_sys(struct bpf_map *map, void *key)

{

	struct sock *sk;



	if (map->value_size != sizeof(u64))

		return ERR_PTR(-ENOSPC);



	sk = __sock_map_lookup_elem(map, *(u32 *)key);

	if (!sk)

		return ERR_PTR(-ENOENT);



	sock_gen_cookie(sk);

	return &sk->sk_cookie;

}



static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test,

			     struct sock **psk)

{
@@ -445,11 +462,18 @@ static bool sock_map_sk_state_allowed(const struct sock *sk) 
static int sock_map_update_elem(struct bpf_map *map, void *key,

				void *value, u64 flags)

{

	u32 ufd = *(u32 *)value;

	u32 idx = *(u32 *)key;

	struct socket *sock;

	struct sock *sk;

	int ret;

	u64 ufd;



	if (map->value_size == sizeof(u64))

		ufd = *(u64 *)value;

	else

		ufd = *(u32 *)value;

	if (ufd > S32_MAX)

		return -EINVAL;



	sock = sockfd_lookup(ufd, &ret);

	if (!sock)
@@ -557,6 +581,7 @@ const struct bpf_map_ops sock_map_ops = { 
	.map_alloc		= sock_map_alloc,

	.map_free		= sock_map_free,

	.map_get_next_key	= sock_map_get_next_key,

	.map_lookup_elem_sys_only = sock_map_lookup_sys,

	.map_update_elem	= sock_map_update_elem,

	.map_delete_elem	= sock_map_delete_elem,

	.map_lookup_elem	= sock_map_lookup,
@@ -787,10 +812,17 @@ out_free: 
static int sock_hash_update_elem(struct bpf_map *map, void *key,

				 void *value, u64 flags)

{

	u32 ufd = *(u32 *)value;

	struct socket *sock;

	struct sock *sk;

	int ret;

	u64 ufd;



	if (map->value_size == sizeof(u64))

		ufd = *(u64 *)value;

	else

		ufd = *(u32 *)value;

	if (ufd > S32_MAX)

		return -EINVAL;



	sock = sockfd_lookup(ufd, &ret);

	if (!sock)
@@ -866,7 +898,8 @@ static struct bpf_map *sock_hash_alloc(union bpf_attr *attr) 
		return ERR_PTR(-EPERM);

	if (attr->max_entries == 0 ||

	    attr->key_size    == 0 ||

	    attr->value_size  != 4 ||

	    (attr->value_size != sizeof(u32) &&

	     attr->value_size != sizeof(u64)) ||

	    attr->map_flags & ~SOCK_CREATE_FLAG_MASK)

		return ERR_PTR(-EINVAL);

	if (attr->key_size > MAX_BPF_STACK)
@@ -943,6 +976,21 @@ static void sock_hash_free(struct bpf_map *map) 
	kfree(htab);

}



static void *sock_hash_lookup_sys(struct bpf_map *map, void *key)

{

	struct sock *sk;



	if (map->value_size != sizeof(u64))

		return ERR_PTR(-ENOSPC);



	sk = __sock_hash_lookup_elem(map, key);

	if (!sk)

		return ERR_PTR(-ENOENT);



	sock_gen_cookie(sk);

	return &sk->sk_cookie;

}



static void sock_hash_release_progs(struct bpf_map *map)

{

	psock_progs_drop(&container_of(map, struct bpf_htab, map)->progs);
@@ -1032,6 +1080,7 @@ const struct bpf_map_ops sock_hash_ops = { 
	.map_update_elem	= sock_hash_update_elem,

	.map_delete_elem	= sock_hash_delete_elem,

	.map_lookup_elem	= sock_map_lookup,

	.map_lookup_elem_sys_only = sock_hash_lookup_sys,

	.map_release_uref	= sock_hash_release_progs,

	.map_check_btf		= map_check_no_btf,

};

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