Commit 98e948fb authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Daniel Borkmann
Browse files

bpf: Allow delete from sockmap/sockhash only if update is allowed 



We have seen an influx of syzkaller reports where a BPF program attached to
a tracepoint triggers a locking rule violation by performing a map_delete
on a sockmap/sockhash.

We don't intend to support this artificial use scenario. Extend the
existing verifier allowed-program-type check for updating sockmap/sockhash
to also cover deleting from a map.

From now on only BPF programs which were previously allowed to update
sockmap/sockhash can delete from these map types.

Fixes: ff910599 ("bpf, sockmap: Prevent lock inversion deadlock in map delete elem")
Reported-by: default avatarTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Reported-by: default avatar <syzbot+ec941d6e24f633a59172@syzkaller.appspotmail.com>
Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: default avatar <syzbot+ec941d6e24f633a59172@syzkaller.appspotmail.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=ec941d6e24f633a59172
Link: https://lore.kernel.org/bpf/20240527-sockmap-verify-deletes-v1-1-944b372f2101@cloudflare.com
parent 95348e46

kernel/bpf/verifier.c

+7 −3
Original line number Diff line number Diff line
@@ -8882,7 +8882,8 @@ static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id) 
	enum bpf_attach_type eatype = env->prog->expected_attach_type;

	enum bpf_prog_type type = resolve_prog_type(env->prog);









	if (func_id != BPF_FUNC_map_update_elem)









	if (func_id != BPF_FUNC_map_update_elem &&









	    func_id != BPF_FUNC_map_delete_elem)









		return false;

















	/* It's not possible to get access to a locked struct sock in these








@@ -8893,6 +8894,11 @@ static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)







		if (eatype == BPF_TRACE_ITER)









			return true;









		break;









	case BPF_PROG_TYPE_SOCK_OPS:









		/* map_update allowed only via dedicated helpers with event type checks */









		if (func_id == BPF_FUNC_map_delete_elem)









			return true;









		break;









	case BPF_PROG_TYPE_SOCKET_FILTER:









	case BPF_PROG_TYPE_SCHED_CLS:









	case BPF_PROG_TYPE_SCHED_ACT:








@@ -8988,7 +8994,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,







	case BPF_MAP_TYPE_SOCKMAP:









		if (func_id != BPF_FUNC_sk_redirect_map &&









		    func_id != BPF_FUNC_sock_map_update &&









		    func_id != BPF_FUNC_map_delete_elem &&









		    func_id != BPF_FUNC_msg_redirect_map &&









		    func_id != BPF_FUNC_sk_select_reuseport &&









		    func_id != BPF_FUNC_map_lookup_elem &&








@@ -8998,7 +9003,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,







	case BPF_MAP_TYPE_SOCKHASH:









		if (func_id != BPF_FUNC_sk_redirect_hash &&









		    func_id != BPF_FUNC_sock_hash_update &&









		    func_id != BPF_FUNC_map_delete_elem &&









		    func_id != BPF_FUNC_msg_redirect_hash &&









		    func_id != BPF_FUNC_sk_select_reuseport &&









		    func_id != BPF_FUNC_map_lookup_elem &&