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authorPaolo Abeni <pabeni@redhat.com>2021-10-07 15:05:00 -0700
committerDavid S. Miller <davem@davemloft.net>2021-10-08 14:55:54 +0100
commit612f71d7328c14369924384ad2170aae2a6abd92 (patch)
tree5c87d9f7ed4048e628eb71ab7b785b879ab1218e /net
parent1da38549dd64c7f5dd22427f12dfa8db3d8a722b (diff)
downloadlinux-612f71d7328c14369924384ad2170aae2a6abd92.tar.bz2
mptcp: fix possible stall on recvmsg()
recvmsg() can enter an infinite loop if the caller provides the MSG_WAITALL, the data present in the receive queue is not sufficient to fulfill the request, and no more data is received by the peer. When the above happens, mptcp_wait_data() will always return with no wait, as the MPTCP_DATA_READY flag checked by such function is set and never cleared in such code path. Leveraging the above syzbot was able to trigger an RCU stall: rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (10499 ticks this GP) idle=0af/1/0x4000000000000000 softirq=10678/10678 fqs=1 (t=10500 jiffies g=13089 q=109) rcu: rcu_preempt kthread starved for 10497 jiffies! g13089 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:28696 pid: 14 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:4955 [inline] __schedule+0x940/0x26f0 kernel/sched/core.c:6236 schedule+0xd3/0x270 kernel/sched/core.c:6315 schedule_timeout+0x14a/0x2a0 kernel/time/timer.c:1881 rcu_gp_fqs_loop+0x186/0x810 kernel/rcu/tree.c:1955 rcu_gp_kthread+0x1de/0x320 kernel/rcu/tree.c:2128 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 8510 Comm: syz-executor827 Not tainted 5.15.0-rc2-next-20210920-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:84 [inline] RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline] RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline] RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline] RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline] RIP: 0010:kasan_check_range+0xc8/0x180 mm/kasan/generic.c:189 Code: 38 00 74 ed 48 8d 50 08 eb 09 48 83 c0 01 48 39 d0 74 7a 80 38 00 74 f2 48 89 c2 b8 01 00 00 00 48 85 d2 75 56 5b 5d 41 5c c3 <48> 85 d2 74 5e 48 01 ea eb 09 48 83 c0 01 48 39 d0 74 50 80 38 00 RSP: 0018:ffffc9000cd676c8 EFLAGS: 00000283 RAX: ffffed100e9a110e RBX: ffffed100e9a110f RCX: ffffffff88ea062a RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff888074d08870 RBP: ffffed100e9a110e R08: 0000000000000001 R09: ffff888074d08877 R10: ffffed100e9a110e R11: 0000000000000000 R12: ffff888074d08000 R13: ffff888074d08000 R14: ffff888074d08088 R15: ffff888074d08000 FS: 0000555556d8e300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 S: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000180 CR3: 0000000068909000 CR4: 00000000001506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: instrument_atomic_read_write include/linux/instrumented.h:101 [inline] test_and_clear_bit include/asm-generic/bitops/instrumented-atomic.h:83 [inline] mptcp_release_cb+0x14a/0x210 net/mptcp/protocol.c:3016 release_sock+0xb4/0x1b0 net/core/sock.c:3204 mptcp_wait_data net/mptcp/protocol.c:1770 [inline] mptcp_recvmsg+0xfd1/0x27b0 net/mptcp/protocol.c:2080 inet6_recvmsg+0x11b/0x5e0 net/ipv6/af_inet6.c:659 sock_recvmsg_nosec net/socket.c:944 [inline] ____sys_recvmsg+0x527/0x600 net/socket.c:2626 ___sys_recvmsg+0x127/0x200 net/socket.c:2670 do_recvmmsg+0x24d/0x6d0 net/socket.c:2764 __sys_recvmmsg net/socket.c:2843 [inline] __do_sys_recvmmsg net/socket.c:2866 [inline] __se_sys_recvmmsg net/socket.c:2859 [inline] __x64_sys_recvmmsg+0x20b/0x260 net/socket.c:2859 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+0x44/0xae RIP: 0033:0x7fc200d2dc39 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc5758e5a8 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fc200d2dc39 RDX: 0000000000000002 RSI: 00000000200017c0 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000f0b5ff R10: 0000000000000100 R11: 0000000000000246 R12: 0000000000000003 R13: 00007ffc5758e5d0 R14: 00007ffc5758e5c0 R15: 0000000000000003 Fix the issue by replacing the MPTCP_DATA_READY bit with direct inspection of the msk receive queue. Reported-and-tested-by: syzbot+3360da629681aa0d22fe@syzkaller.appspotmail.com Fixes: 7a6a6cbc3e59 ("mptcp: recvmsg() can drain data from multiple subflow") 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>
Diffstat (limited to 'net')
-rw-r--r--net/mptcp/protocol.c55
1 files changed, 15 insertions, 40 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e5df0b5971c8..d073b2111382 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -528,7 +528,6 @@ static bool mptcp_check_data_fin(struct sock *sk)
sk->sk_shutdown |= RCV_SHUTDOWN;
smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
- set_bit(MPTCP_DATA_READY, &msk->flags);
switch (sk->sk_state) {
case TCP_ESTABLISHED:
@@ -742,10 +741,9 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
/* Wake-up the reader only for in-sequence data */
mptcp_data_lock(sk);
- if (move_skbs_to_msk(msk, ssk)) {
- set_bit(MPTCP_DATA_READY, &msk->flags);
+ if (move_skbs_to_msk(msk, ssk))
sk->sk_data_ready(sk);
- }
+
mptcp_data_unlock(sk);
}
@@ -847,7 +845,6 @@ static void mptcp_check_for_eof(struct mptcp_sock *msk)
sk->sk_shutdown |= RCV_SHUTDOWN;
smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
- set_bit(MPTCP_DATA_READY, &msk->flags);
sk->sk_data_ready(sk);
}
@@ -1759,21 +1756,6 @@ out:
return copied ? : ret;
}
-static void mptcp_wait_data(struct sock *sk, long *timeo)
-{
- DEFINE_WAIT_FUNC(wait, woken_wake_function);
- struct mptcp_sock *msk = mptcp_sk(sk);
-
- add_wait_queue(sk_sleep(sk), &wait);
- sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
-
- sk_wait_event(sk, timeo,
- test_bit(MPTCP_DATA_READY, &msk->flags), &wait);
-
- sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
- remove_wait_queue(sk_sleep(sk), &wait);
-}
-
static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
struct msghdr *msg,
size_t len, int flags,
@@ -2077,19 +2059,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
}
pr_debug("block timeout %ld", timeo);
- mptcp_wait_data(sk, &timeo);
- }
-
- if (skb_queue_empty_lockless(&sk->sk_receive_queue) &&
- skb_queue_empty(&msk->receive_queue)) {
- /* entire backlog drained, clear DATA_READY. */
- clear_bit(MPTCP_DATA_READY, &msk->flags);
-
- /* .. race-breaker: ssk might have gotten new data
- * after last __mptcp_move_skbs() returned false.
- */
- if (unlikely(__mptcp_move_skbs(msk)))
- set_bit(MPTCP_DATA_READY, &msk->flags);
+ sk_wait_data(sk, &timeo, NULL);
}
out_err:
@@ -2098,9 +2068,9 @@ out_err:
tcp_recv_timestamp(msg, sk, &tss);
}
- pr_debug("msk=%p data_ready=%d rx queue empty=%d copied=%d",
- msk, test_bit(MPTCP_DATA_READY, &msk->flags),
- skb_queue_empty_lockless(&sk->sk_receive_queue), copied);
+ pr_debug("msk=%p rx queue empty=%d:%d copied=%d",
+ msk, skb_queue_empty_lockless(&sk->sk_receive_queue),
+ skb_queue_empty(&msk->receive_queue), copied);
if (!(flags & MSG_PEEK))
mptcp_rcv_space_adjust(msk, copied);
@@ -2368,7 +2338,6 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
inet_sk_state_store(sk, TCP_CLOSE);
sk->sk_shutdown = SHUTDOWN_MASK;
smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
- set_bit(MPTCP_DATA_READY, &msk->flags);
set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
mptcp_close_wake_up(sk);
@@ -3385,8 +3354,14 @@ unlock_fail:
static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
{
- return test_bit(MPTCP_DATA_READY, &msk->flags) ? EPOLLIN | EPOLLRDNORM :
- 0;
+ /* Concurrent splices from sk_receive_queue into receive_queue will
+ * always show at least one non-empty queue when checked in this order.
+ */
+ if (skb_queue_empty_lockless(&((struct sock *)msk)->sk_receive_queue) &&
+ skb_queue_empty_lockless(&msk->receive_queue))
+ return 0;
+
+ return EPOLLIN | EPOLLRDNORM;
}
static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
@@ -3421,7 +3396,7 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
state = inet_sk_state_load(sk);
pr_debug("msk=%p state=%d flags=%lx", msk, state, msk->flags);
if (state == TCP_LISTEN)
- return mptcp_check_readable(msk);
+ return test_bit(MPTCP_DATA_READY, &msk->flags) ? EPOLLIN | EPOLLRDNORM : 0;
if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
mask |= mptcp_check_readable(msk);