Commit 54fedb42 authored by John Fastabend's avatar John Fastabend Committed by Daniel Borkmann
Browse files

bpf: sockmap, fix smap_list_map_remove when psock is in many maps 



If a hashmap is free'd with open socks it removes the reference to
the hash entry from the psock. If that is the last reference to the
psock then it will also be free'd by the reference counting logic.
However the current logic that removes the hash reference from the
list of references is broken. In smap_list_remove() we first check
if the sockmap entry matches and then check if the hashmap entry
matches. But, the sockmap entry sill always match because its NULL in
this case which causes the first entry to be removed from the list.
If this is always the "right" entry (because the user adds/removes
entries in order) then everything is OK but otherwise a subsequent
bpf_tcp_close() may reference a free'd object.

To fix this create two list handlers one for sockmap and one for
sockhash.

Reported-by: default avatar <syzbot+0ce137753c78f7b6acc1@syzkaller.appspotmail.com>
Fixes: 81110384 ("bpf: sockmap, add hash map support")
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 9901c5d7

kernel/bpf/sockmap.c

+22 −12
Original line number Diff line number Diff line
@@ -1602,18 +1602,28 @@ free_stab: 
	return ERR_PTR(err);

}



static void smap_list_remove(struct smap_psock *psock,

			     struct sock **entry,

			     struct htab_elem *hash_link)

static void smap_list_map_remove(struct smap_psock *psock,

				 struct sock **entry)

{

	struct smap_psock_map_entry *e, *tmp;



	list_for_each_entry_safe(e, tmp, &psock->maps, list) {

		if (e->entry == entry || e->hash_link == hash_link) {

		if (e->entry == entry)

			list_del(&e->list);

			break;

	}

}



static void smap_list_hash_remove(struct smap_psock *psock,

				  struct htab_elem *hash_link)

{

	struct smap_psock_map_entry *e, *tmp;



	list_for_each_entry_safe(e, tmp, &psock->maps, list) {

		struct htab_elem *c = e->hash_link;



		if (c == hash_link)

			list_del(&e->list);

	}

}



static void sock_map_free(struct bpf_map *map)
@@ -1647,7 +1657,7 @@ static void sock_map_free(struct bpf_map *map) 
		 * to be null and queued for garbage collection.

		 */

		if (likely(psock)) {

			smap_list_remove(psock, &stab->sock_map[i], NULL);

			smap_list_map_remove(psock, &stab->sock_map[i]);

			smap_release_sock(psock, sock);

		}

		write_unlock_bh(&sock->sk_callback_lock);
@@ -1706,7 +1716,7 @@ static int sock_map_delete_elem(struct bpf_map *map, void *key) 


	if (psock->bpf_parse)

		smap_stop_sock(psock, sock);

	smap_list_remove(psock, &stab->sock_map[k], NULL);

	smap_list_map_remove(psock, &stab->sock_map[k]);

	smap_release_sock(psock, sock);

out:

	write_unlock_bh(&sock->sk_callback_lock);
@@ -1908,7 +1918,7 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops, 
		struct smap_psock *opsock = smap_psock_sk(osock);



		write_lock_bh(&osock->sk_callback_lock);

		smap_list_remove(opsock, &stab->sock_map[i], NULL);

		smap_list_map_remove(opsock, &stab->sock_map[i]);

		smap_release_sock(opsock, osock);

		write_unlock_bh(&osock->sk_callback_lock);

	}
@@ -2142,7 +2152,7 @@ static void sock_hash_free(struct bpf_map *map) 
			 * (psock) to be null and queued for garbage collection.

			 */

			if (likely(psock)) {

				smap_list_remove(psock, NULL, l);

				smap_list_hash_remove(psock, l);

				smap_release_sock(psock, sock);

			}

			write_unlock_bh(&sock->sk_callback_lock);
@@ -2322,7 +2332,7 @@ static int sock_hash_ctx_update_elem(struct bpf_sock_ops_kern *skops, 
		psock = smap_psock_sk(l_old->sk);



		hlist_del_rcu(&l_old->hash_node);

		smap_list_remove(psock, NULL, l_old);

		smap_list_hash_remove(psock, l_old);

		smap_release_sock(psock, l_old->sk);

		free_htab_elem(htab, l_old);

	}
@@ -2390,7 +2400,7 @@ static int sock_hash_delete_elem(struct bpf_map *map, void *key) 
		 * to be null and queued for garbage collection.

		 */

		if (likely(psock)) {

			smap_list_remove(psock, NULL, l);

			smap_list_hash_remove(psock, l);

			smap_release_sock(psock, sock);

		}

		write_unlock_bh(&sock->sk_callback_lock);

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