bpf: Allow delete from sockmap/sockhash only if update is allowed
[ Upstream commit 98e948fb60d41447fd8d2d0c3b8637fc6b6dc26d ]
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.
BUG=b/349317653
TEST=presubmit
RELEASE_NOTE=Fixes CVE-2024-38662 in the Linux kernel
cos-patch: security-moderate
Fixes: ff9105993240 ("bpf, sockmap: Prevent lock inversion deadlock in map delete elem")
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Reported-by: syzbot+ec941d6e24f633a59172@syzkaller.appspotmail.com
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: syzbot+ec941d6e24f633a59172@syzkaller.appspotmail.com
Acked-by: John 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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
Change-Id: Ic2b02f7f5f64ab2af7f16b987c2befd270ed2d9d
Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/75054
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Arnav Kansal <rnv@google.com>
Reviewed-by: Kevin Berry <kpberry@google.com>
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 33fb379..8abea44 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5564,7 +5564,8 @@ 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
@@ -5575,6 +5576,11 @@ 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:
@@ -5662,7 +5668,6 @@ 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 &&
@@ -5672,7 +5677,6 @@ 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 &&
