From: Martin KaFai Lau <kafai@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>,
<netdev@vger.kernel.org>, James Chapman <jchapman@katalix.com>
Subject: [PATCH v2 bpf 2/2] bpf: net: Avoid incorrect bpf_sk_reuseport_detach call
Date: Wed, 8 Jul 2020 23:11:10 -0700 [thread overview]
Message-ID: <20200709061110.4019316-1-kafai@fb.com> (raw)
In-Reply-To: <20200709061057.4018499-1-kafai@fb.com>
bpf_sk_reuseport_detach is currently called when sk->sk_user_data
is not NULL. It is incorrect because sk->sk_user_data may not be
managed by the bpf's reuseport_array. It has been reported in [1] that,
the bpf_sk_reuseport_detach() which is called from udp_lib_unhash() has
corrupted the sk_user_data managed by l2tp.
This patch solves it by using another bit (defined as SK_USER_DATA_BPF)
of the sk_user_data pointer value. It marks that a sk_user_data is
managed/owned by BPF.
The patch depends on a PTRMASK introduced in
commit f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if tagged").
[ Note: sk->sk_user_data is used by bpf's reuseport_array only when a sk is
added to the bpf's reuseport_array.
i.e. doing setsockopt(SO_REUSEPORT) and having "sk->sk_reuseport == 1"
alone will not stop sk->sk_user_data being used by other means. ]
[1]: https://lore.kernel.org/netdev/20200706121259.GA20199@katalix.com/
Reported-by: James Chapman <jchapman@katalix.com>
Cc: James Chapman <jchapman@katalix.com>
Fixes: 5dc4c4b7d4e8 ("bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
include/net/sock.h | 3 ++-
kernel/bpf/reuseport_array.c | 5 +++--
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 3428619faae4..1183507df95b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -533,7 +533,8 @@ enum sk_pacing {
* be copied.
*/
#define SK_USER_DATA_NOCOPY 1UL
-#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY)
+#define SK_USER_DATA_BPF 2UL /* Managed by BPF */
+#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY | SK_USER_DATA_BPF)
/**
* sk_user_data_is_nocopy - Test if sk_user_data pointer must not be copied
diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c
index a95bc8d7e812..cae9d505e04a 100644
--- a/kernel/bpf/reuseport_array.c
+++ b/kernel/bpf/reuseport_array.c
@@ -24,7 +24,7 @@ void bpf_sk_reuseport_detach(struct sock *sk)
write_lock_bh(&sk->sk_callback_lock);
sk_user_data = (uintptr_t)sk->sk_user_data;
- if (sk_user_data) {
+ if (sk_user_data & SK_USER_DATA_BPF) {
struct sock __rcu **socks;
socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
@@ -309,7 +309,8 @@ int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
if (err)
goto put_file_unlock;
- sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY;
+ sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
+ SK_USER_DATA_BPF;
WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
rcu_assign_pointer(array->ptrs[index], nsk);
free_osk = osk;
--
2.24.1
next prev parent reply other threads:[~2020-07-09 6:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 6:10 [PATCH v2 bpf 0/2] bpf: net: Fixes in sk_user_data of reuseport_array Martin KaFai Lau
2020-07-09 6:11 ` [PATCH v2 bpf 1/2] bpf: net: Avoid copying sk_user_data of reuseport_array during sk_clone Martin KaFai Lau
2020-07-09 16:46 ` Jakub Sitnicki
2020-07-09 20:07 ` Daniel Borkmann
2020-07-09 21:27 ` Martin KaFai Lau
2020-07-09 6:11 ` Martin KaFai Lau [this message]
2020-07-09 10:58 ` [PATCH v2 bpf 2/2] bpf: net: Avoid incorrect bpf_sk_reuseport_detach call James Chapman
2020-07-09 18:47 ` Martin KaFai Lau
2020-07-09 20:07 ` [PATCH v2 bpf 0/2] bpf: net: Fixes in sk_user_data of reuseport_array Daniel Borkmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200709061110.4019316-1-kafai@fb.com \
--to=kafai@fb.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=jchapman@katalix.com \
--cc=kernel-team@fb.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).