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 @@ -281,7 +281,8 @@ 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_queue_msg(struct sk_psock *psock, --- a/include/net/sock.h +++ b/include/net/sock.h @@ -527,14 +527,26 @@ 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 @@ -547,24 +559,40 @@ 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)
/* * SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -612,7 +612,9 @@ 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);
out: