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").
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>
---
v2 -> v3:
- use SK_USER_DATA_PSOCK instead of SK_USER_DATA_NOTPSOCK
to patch the bug
- refactor the code on assigning to sk_user_data field
in psock part
- refactor the code on getting and setting the flag
with sk_user_data field
v1 -> v2:
- add bit in PTRMASK to patch the bug
include/linux/skmsg.h | 2 +-
include/net/sock.h | 58 +++++++++++++++++++++++++++++++------------
net/core/skmsg.c | 3 ++-
3 files changed, 45 insertions(+), 18 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..d010910d5879 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -545,14 +545,24 @@ 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 - Managed by BPF
+ *
+ * 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
@@ -570,19 +580,35 @@ static inline bool sk_user_data_is_nocopy(const struct sock *sk)
void *__tmp = rcu_dereference(__sk_user_data((sk))); \ (void *)((uintptr_t)__tmp & SK_USER_DATA_PTRMASK); \
})
-#define rcu_assign_sk_user_data(sk, ptr) \
+#define rcu_assign_sk_user_data_with_flags(sk, ptr, flags) \
({ \
- 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)
+
+/**
+ * rcu_dereference_sk_user_data_psock - return psock if sk_user_data
+ * points to the psock type(SK_USER_DATA_PSOCK flag is set), otherwise
+ * return NULL
+ *
+ * @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_PSOCK)
+ return (struct sk_psock *)(__tmp & SK_USER_DATA_PTRMASK);
+
+ return NULL;
+}
static inline
struct net *sock_net(const struct sock *sk)
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index b0fcd0200e84..d174897dbb4b 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -735,7 +735,8 @@ struct sk_psock *sk_psock_init(struct sock *sk, int node)
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);
out:
--
2.25.1
