| Message ID | 20220803080338.166730-1-yin31149@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3] net/smc: fix refcount bug in sk_psock_get (2) | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Guessing tree name failed - patch did not apply, async |
On 2022/8/3 16:03, Hawkins Jiawei wrote: > 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@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> > --- > 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(-) > Hi Hawkins, Since the fix v3 doesn't involved smc codes any more, I wonder if it's still appropriate to use 'net/smc:' in subject? Cheers, Wen Gu
On Wed, 3 Aug 2022 at 19:27, Wen Gu <guwen@linux.alibaba.com> wrote: > Hi Hawkins, > > Since the fix v3 doesn't involved smc codes any more, I wonder if it's still > appropriate to use 'net/smc:' in subject? > > Cheers, > Wen Gu Thank you for reminding me, I will send the v4 patch with new subject.
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:
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@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> --- 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(-)