[PATCH v2] net/smc: fix refcount bug in sk_psock_get (2)
From: Hawkins Jiawei
Date: Sat Jul 30 2022 - 04:59:08 EST
Syzkaller reports refcount bug as follows:
------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: CPU: 1 PID: 3605 at lib/refcount.c:19 refcount_warn_saturate+0xf4/0x1e0 lib/refcount.c:19
Modules linked in:
CPU: 1 PID: 3605 Comm: syz-executor208 Not tainted 5.18.0-syzkaller-03023-g7e062cda7d90 #0
...
Call Trace:
<TASK>
__refcount_add_not_zero include/linux/refcount.h:163 [inline]
__refcount_inc_not_zero include/linux/refcount.h:227 [inline]
refcount_inc_not_zero include/linux/refcount.h:245 [inline]
sk_psock_get+0x3bc/0x410 include/linux/skmsg.h:439
tls_data_ready+0x6d/0x1b0 net/tls/tls_sw.c:2091
tcp_data_ready+0x106/0x520 net/ipv4/tcp_input.c:4983
tcp_data_queue+0x25f2/0x4c90 net/ipv4/tcp_input.c:5057
tcp_rcv_state_process+0x1774/0x4e80 net/ipv4/tcp_input.c:6659
tcp_v4_do_rcv+0x339/0x980 net/ipv4/tcp_ipv4.c:1682
sk_backlog_rcv include/net/sock.h:1061 [inline]
__release_sock+0x134/0x3b0 net/core/sock.c:2849
release_sock+0x54/0x1b0 net/core/sock.c:3404
inet_shutdown+0x1e0/0x430 net/ipv4/af_inet.c:909
__sys_shutdown_sock net/socket.c:2331 [inline]
__sys_shutdown_sock net/socket.c:2325 [inline]
__sys_shutdown+0xf1/0x1b0 net/socket.c:2343
__do_sys_shutdown net/socket.c:2351 [inline]
__se_sys_shutdown net/socket.c:2349 [inline]
__x64_sys_shutdown+0x50/0x70 net/socket.c:2349
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
</TASK>
During SMC fallback process in connect syscall, kernel will
replaces TCP with SMC. In order to forward wakeup
smc socket waitqueue after fallback, kernel will sets
clcsk->sk_user_data to origin smc socket in
smc_fback_replace_callbacks().
Later, in shutdown syscall, kernel will calls
sk_psock_get(), which treats the clcsk->sk_user_data
as sk_psock type, triggering the refcnt warning.
So, the root cause is that smc and psock, both will use
sk_user_data field. So they will mismatch this field
easily.
This patch solves it by using another bit(defined as
SK_USER_DATA_NOTPSOCK) in PTRMASK, to mark whether
sk_user_data points to a sk_psock object or not.
This patch depends on a PTRMASK introduced in commit f1ff5ce2cd5e
("net, sk_msg: Clear sk_user_data pointer on clone if tagged").
Fixes: 341adeec9ada ("net/smc: Forward wakeup to smc socket waitqueue after fallback")
Fixes: a60a2b1e0af1 ("net/smc: reduce active tcp_listen workers")
Reported-and-tested-by: syzbot+5f26f85569bd179c18ce@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Acked-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
---
v1 -> v2:
- add bit in PTRMASK to patch the bug
include/linux/skmsg.h | 2 +-
include/net/sock.h | 27 +++++++++++++++++++++++++--
net/smc/af_smc.c | 6 ++++--
net/smc/smc.h | 2 +-
4 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index c5a2d6f50f25..81bfa1a33623 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -277,7 +277,7 @@ static inline void sk_msg_sg_copy_clear(struct sk_msg *msg, u32 start)
static inline struct sk_psock *sk_psock(const struct sock *sk)
{
- return rcu_dereference_sk_user_data(sk);
+ return rcu_dereference_sk_user_data_psock(sk);
}
static inline void sk_psock_set_state(struct sk_psock *psock,
diff --git a/include/net/sock.h b/include/net/sock.h
index 9fa54762e077..316c0313b2bf 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -549,10 +549,17 @@ enum sk_pacing {
* when cloning the socket. For instance, it can point to a reference
* counted object. sk_user_data bottom bit is set if pointer must not
* be copied.
+ *
+ * SK_USER_DATA_NOCOPY - test if pointer must not copied
+ * SK_USER_DATA_BPF - managed by BPF
+ * SK_USER_DATA_NOTPSOCK - test if pointer points to psock
*/
#define SK_USER_DATA_NOCOPY 1UL
-#define SK_USER_DATA_BPF 2UL /* Managed by BPF */
-#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY | SK_USER_DATA_BPF)
+#define SK_USER_DATA_BPF 2UL
+#define SK_USER_DATA_NOTPSOCK 4UL
+#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY | SK_USER_DATA_BPF |\
+ SK_USER_DATA_NOTPSOCK)
+
/**
* sk_user_data_is_nocopy - Test if sk_user_data pointer must not be copied
@@ -584,6 +591,22 @@ static inline bool sk_user_data_is_nocopy(const struct sock *sk)
__tmp | SK_USER_DATA_NOCOPY); \
})
+/**
+ * rcu_dereference_sk_user_data_psock - return psock if sk_user_data points
+ * to the psock
+ * @sk: socket
+ */
+static inline
+struct sk_psock *rcu_dereference_sk_user_data_psock(const struct sock *sk)
+{
+ uintptr_t __tmp = (uintptr_t)rcu_dereference(__sk_user_data((sk)));
+
+ if (__tmp & SK_USER_DATA_NOTPSOCK)
+ return NULL;
+ return (struct sk_psock *)(__tmp & SK_USER_DATA_PTRMASK);
+}
+
+
static inline
struct net *sock_net(const struct sock *sk)
{
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 433bb5a7df31..d0feccf824c8 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -812,7 +812,8 @@ static void smc_fback_replace_callbacks(struct smc_sock *smc)
struct sock *clcsk = smc->clcsock->sk;
write_lock_bh(&clcsk->sk_callback_lock);
- clcsk->sk_user_data = (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+ clcsk->sk_user_data = (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY |
+ SK_USER_DATA_NOTPSOCK);
smc_clcsock_replace_cb(&clcsk->sk_state_change, smc_fback_state_change,
&smc->clcsk_state_change);
@@ -2470,7 +2471,8 @@ static int smc_listen(struct socket *sock, int backlog)
*/
write_lock_bh(&smc->clcsock->sk->sk_callback_lock);
smc->clcsock->sk->sk_user_data =
- (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+ (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY |
+ SK_USER_DATA_NOTPSOCK);
smc_clcsock_replace_cb(&smc->clcsock->sk->sk_data_ready,
smc_clcsock_data_ready, &smc->clcsk_data_ready);
write_unlock_bh(&smc->clcsock->sk->sk_callback_lock);
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 5ed765ea0c73..c24d0469d267 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -299,7 +299,7 @@ static inline void smc_init_saved_callbacks(struct smc_sock *smc)
static inline struct smc_sock *smc_clcsock_user_data(const struct sock *clcsk)
{
return (struct smc_sock *)
- ((uintptr_t)clcsk->sk_user_data & ~SK_USER_DATA_NOCOPY);
+ ((uintptr_t)clcsk->sk_user_data & SK_USER_DATA_PTRMASK);
}
/* save target_cb in saved_cb, and replace target_cb with new_cb */
--
2.25.1