* [PATCH bpf 1/2] bpf: net: Avoid copying sk_user_data of reuseport_array during sk_clone
2020-07-08 1:44 [PATCH bpf 0/2] bpf: net: Fixes in sk_user_data of reuseport_array Martin KaFai Lau
@ 2020-07-08 1:44 ` Martin KaFai Lau
2020-07-08 1:44 ` [PATCH bpf 2/2] bpf: net: Avoid incorrect bpf_sk_reuseport_detach call Martin KaFai Lau
1 sibling, 0 replies; 4+ messages in thread
From: Martin KaFai Lau @ 2020-07-08 1:44 UTC (permalink / raw)
To: bpf; +Cc: Alexei Starovoitov, Daniel Borkmann, kernel-team, netdev
It makes little sense for copying sk_user_data of reuseport_array during
sk_clone_lock(). This patch reuses the SK_USER_DATA_NOCOPY bit introduced in
commit f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if tagged").
It is used to mark the sk_user_data is not supposed to be copied to its clone.
Although the cloned sk's sk_user_data will not be used/freed in
bpf_sk_reuseport_detach(), this change can still allow the cloned
sk's sk_user_data to be used by some other means.
Freeing the reuseport_array's sk_user_data does not require a rcu grace
period. Thus, the existing rcu_assign_sk_user_data_nocopy() is not
used.
Fixes: 5dc4c4b7d4e8 ("bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
kernel/bpf/reuseport_array.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c
index 21cde24386db..a95bc8d7e812 100644
--- a/kernel/bpf/reuseport_array.c
+++ b/kernel/bpf/reuseport_array.c
@@ -20,11 +20,14 @@ static struct reuseport_array *reuseport_array(struct bpf_map *map)
/* The caller must hold the reuseport_lock */
void bpf_sk_reuseport_detach(struct sock *sk)
{
- struct sock __rcu **socks;
+ uintptr_t sk_user_data;
write_lock_bh(&sk->sk_callback_lock);
- socks = sk->sk_user_data;
- if (socks) {
+ sk_user_data = (uintptr_t)sk->sk_user_data;
+ if (sk_user_data) {
+ struct sock __rcu **socks;
+
+ socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
WRITE_ONCE(sk->sk_user_data, NULL);
/*
* Do not move this NULL assignment outside of
@@ -252,6 +255,7 @@ int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
struct sock *free_osk = NULL, *osk, *nsk;
struct sock_reuseport *reuse;
u32 index = *(u32 *)key;
+ uintptr_t sk_user_data;
struct socket *socket;
int err, fd;
@@ -305,7 +309,8 @@ int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
if (err)
goto put_file_unlock;
- WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
+ sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY;
+ WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
rcu_assign_pointer(array->ptrs[index], nsk);
free_osk = osk;
err = 0;
--
2.24.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH bpf 2/2] bpf: net: Avoid incorrect bpf_sk_reuseport_detach call
2020-07-08 1:44 [PATCH bpf 0/2] bpf: net: Fixes in sk_user_data of reuseport_array Martin KaFai Lau
2020-07-08 1:44 ` [PATCH bpf 1/2] bpf: net: Avoid copying sk_user_data of reuseport_array during sk_clone Martin KaFai Lau
@ 2020-07-08 1:44 ` Martin KaFai Lau
2020-07-08 5:45 ` Andrii Nakryiko
1 sibling, 1 reply; 4+ messages in thread
From: Martin KaFai Lau @ 2020-07-08 1:44 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, kernel-team, netdev, James Chapman
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 report 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..9fe42c890706 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 ~3UL
/**
* 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
^ permalink raw reply related [flat|nested] 4+ messages in thread