[PATCH 5.19 14/72] net: fix refcount bug in sk_psock_get (2)

Greg Kroah-Hartman
2022-09-02T13:33:07Z

From: Hawkins Jiawei <yin31149@gmail.com>

commit 2a0133723f9ebeb751cfce19f74ec07e108bef1f upstream.

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
<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 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_PSOCK) in PTRMASK, to mark whether
sk_user_data points to a 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").

For there will possibly be more flags in the sk_user_data field,
this patch also refactor sk_user_data flags code to be more generic
to improve its maintainability.

Reported-and-tested-by: syzbot+5f26f85569bd179c18ce@syzkaller.appspotmail.com
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Wen Gu <guwen@linux.alibaba.com>
Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/skmsg.h | 3 +-
include/net/sock.h | 68 +++++++++++++++++++++++++++++++++++---------------
net/core/skmsg.c | 4 ++
3 files changed, 53 insertions(+), 22 deletions(-)

--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -277,7 +277,8 @@ static inline void sk_msg_sg_copy_clear(

static inline struct sk_psock *sk_psock(const struct sock *sk)
{
- return rcu_dereference_sk_user_data(sk);
+ return __rcu_dereference_sk_user_data_with_flags(sk,
+ SK_USER_DATA_PSOCK);
}

static inline void sk_psock_set_state(struct sk_psock *psock,
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -545,14 +545,26 @@ enum sk_pacing {
SK_PACING_FQ = 2,
};

-/* Pointer stored in sk_user_data might not be suitable for copying
- * 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.
+/* flag bits in sk_user_data
+ *
+ * - SK_USER_DATA_NOCOPY: Pointer stored in sk_user_data might
+ * not be suitable for copying 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_BPF: Mark whether sk_user_data field is
+ * managed/owned by a BPF reuseport array. This bit should be set
+ * when sk_user_data's sk is added to the bpf's reuseport_array.
+ *
+ * - SK_USER_DATA_PSOCK: Mark whether pointer stored in
+ * sk_user_data points to psock type. This bit should be set
+ * when sk_user_data is assigned to a psock object.
*/
#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_PSOCK 4UL
+#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY | SK_USER_DATA_BPF |\
+ SK_USER_DATA_PSOCK)

/**
* sk_user_data_is_nocopy - Test if sk_user_data pointer must not be copied
@@ -565,24 +577,40 @@ static inline bool sk_user_data_is_nocop

#define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data)))

+/**
+ * __rcu_dereference_sk_user_data_with_flags - return the pointer
+ * only if argument flags all has been set in sk_user_data. Otherwise
+ * return NULL
+ *
+ * @sk: socket
+ * @flags: flag bits
+ */
+static inline void *
+__rcu_dereference_sk_user_data_with_flags(const struct sock *sk,
+ uintptr_t flags)
+{
+ uintptr_t sk_user_data = (uintptr_t)rcu_dereference(__sk_user_data(sk));
+
+ WARN_ON_ONCE(flags & SK_USER_DATA_PTRMASK);
+
+ if ((sk_user_data & flags) == flags)
+ return (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
+ return NULL;
+}
+
#define rcu_dereference_sk_user_data(sk) \
+ __rcu_dereference_sk_user_data_with_flags(sk, 0)
+#define __rcu_assign_sk_user_data_with_flags(sk, ptr, flags) \
({ \
- void *__tmp = rcu_dereference(__sk_user_data((sk))); \
- (void *)((uintptr_t)__tmp & SK_USER_DATA_PTRMASK); \
-})
-#define rcu_assign_sk_user_data(sk, ptr) \
-({ \
- uintptr_t __tmp = (uintptr_t)(ptr); \
- WARN_ON_ONCE(__tmp & ~SK_USER_DATA_PTRMASK); \
- rcu_assign_pointer(__sk_user_data((sk)), __tmp); \
-})
-#define rcu_assign_sk_user_data_nocopy(sk, ptr) \
-({ \
- uintptr_t __tmp = (uintptr_t)(ptr); \
- WARN_ON_ONCE(__tmp & ~SK_USER_DATA_PTRMASK); \
+ uintptr_t __tmp1 = (uintptr_t)(ptr), \
+ __tmp2 = (uintptr_t)(flags); \
+ WARN_ON_ONCE(__tmp1 & ~SK_USER_DATA_PTRMASK); \
+ WARN_ON_ONCE(__tmp2 & SK_USER_DATA_PTRMASK); \
rcu_assign_pointer(__sk_user_data((sk)), \
- __tmp | SK_USER_DATA_NOCOPY); \
+ __tmp1 | __tmp2); \
})
+#define rcu_assign_sk_user_data(sk, ptr) \
+ __rcu_assign_sk_user_data_with_flags(sk, ptr, 0)

static inline
struct net *sock_net(const struct sock *sk)
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -735,7 +735,9 @@ struct sk_psock *sk_psock_init(struct so
sk_psock_set_state(psock, SK_PSOCK_TX_ENABLED);
refcount_set(&psock->refcnt, 1);

- rcu_assign_sk_user_data_nocopy(sk, psock);
+ __rcu_assign_sk_user_data_with_flags(sk, psock,
+ SK_USER_DATA_NOCOPY |
+ SK_USER_DATA_PSOCK);
sock_hold(sk);