From: Paolo Abeni pabeni@redhat.com
commit c886d70286bf3ad411eb3d689328a67f7102c6ae upstream.
Dipanjan reported a syzbot splat at close time:
WARNING: CPU: 1 PID: 10818 at net/ipv4/af_inet.c:153 inet_sock_destruct+0x6d0/0x8e0 net/ipv4/af_inet.c:153 Modules linked in: uio_ivshmem(OE) uio(E) CPU: 1 PID: 10818 Comm: kworker/1:16 Tainted: G OE 5.19.0-rc6-g2eae0556bb9d #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Workqueue: events mptcp_worker RIP: 0010:inet_sock_destruct+0x6d0/0x8e0 net/ipv4/af_inet.c:153 Code: 21 02 00 00 41 8b 9c 24 28 02 00 00 e9 07 ff ff ff e8 34 4d 91 f9 89 ee 4c 89 e7 e8 4a 47 60 ff e9 a6 fc ff ff e8 20 4d 91 f9 <0f> 0b e9 84 fe ff ff e8 14 4d 91 f9 0f 0b e9 d4 fd ff ff e8 08 4d RSP: 0018:ffffc9001b35fa78 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00000000002879d0 RCX: ffff8881326f3b00 RDX: 0000000000000000 RSI: ffff8881326f3b00 RDI: 0000000000000002 RBP: ffff888179662674 R08: ffffffff87e983a0 R09: 0000000000000000 R10: 0000000000000005 R11: 00000000000004ea R12: ffff888179662400 R13: ffff888179662428 R14: 0000000000000001 R15: ffff88817e38e258 FS: 0000000000000000(0000) GS:ffff8881f5f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020007bc0 CR3: 0000000179592000 CR4: 0000000000150ee0 Call Trace: <TASK> __sk_destruct+0x4f/0x8e0 net/core/sock.c:2067 sk_destruct+0xbd/0xe0 net/core/sock.c:2112 __sk_free+0xef/0x3d0 net/core/sock.c:2123 sk_free+0x78/0xa0 net/core/sock.c:2134 sock_put include/net/sock.h:1927 [inline] __mptcp_close_ssk+0x50f/0x780 net/mptcp/protocol.c:2351 __mptcp_destroy_sock+0x332/0x760 net/mptcp/protocol.c:2828 mptcp_worker+0x5d2/0xc90 net/mptcp/protocol.c:2586 process_one_work+0x9cc/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302 </TASK>
The root cause of the problem is that an mptcp-level (re)transmit can race with mptcp_close() and the packet scheduler checks the subflow state before acquiring the socket lock: we can try to (re)transmit on an already closed ssk.
Fix the issue checking again the subflow socket status under the subflow socket lock protection. Additionally add the missing check for the fallback-to-tcp case.
Fixes: d5f49190def6 ("mptcp: allow picking different xmit subflows") Reported-by: Dipanjan Das mail.dipanjan.das@gmail.com Reviewed-by: Mat Martineau mathew.j.martineau@linux.intel.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Mat Martineau mathew.j.martineau@linux.intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/protocol.c | 8 +++++++- net/mptcp/protocol.h | 11 +++++++---- 2 files changed, 14 insertions(+), 5 deletions(-)
--- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1276,6 +1276,9 @@ static int mptcp_sendmsg_frag(struct soc info->limit > dfrag->data_len)) return 0;
+ if (unlikely(!__tcp_can_send(ssk))) + return -EAGAIN; + /* compute send limit */ info->mss_now = tcp_send_mss(ssk, &info->size_goal, info->flags); copy = info->size_goal; @@ -1449,7 +1452,8 @@ static struct sock *mptcp_subflow_get_se if (__mptcp_check_fallback(msk)) { if (!msk->first) return NULL; - return sk_stream_memory_free(msk->first) ? msk->first : NULL; + return __tcp_can_send(msk->first) && + sk_stream_memory_free(msk->first) ? msk->first : NULL; }
/* re-use last subflow, if the burst allow that */ @@ -1600,6 +1604,8 @@ void __mptcp_push_pending(struct sock *s
ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info); if (ret <= 0) { + if (ret == -EAGAIN) + continue; mptcp_push_release(ssk, &info); goto out; } --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -625,16 +625,19 @@ void mptcp_info2sockaddr(const struct mp struct sockaddr_storage *addr, unsigned short family);
-static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow) +static inline bool __tcp_can_send(const struct sock *ssk) { - struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + /* only send if our side has not closed yet */ + return ((1 << inet_sk_state_load(ssk)) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)); +}
+static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow) +{ /* can't send if JOIN hasn't completed yet (i.e. is usable for mptcp) */ if (subflow->request_join && !subflow->fully_established) return false;
- /* only send if our side has not closed yet */ - return ((1 << ssk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)); + return __tcp_can_send(mptcp_subflow_tcp_sock(subflow)); }
void mptcp_subflow_set_active(struct mptcp_subflow_context *subflow);