unix: return zero if peer is closed
Previously, recvmsg() on a unix stream socket with its peer closed will never return, with goroutine call trace like this: ... 2 in gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).block at pkg/sentry/kernel/task_block.go:124 3 in gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).BlockWithDeadline at pkg/sentry/kernel/task_block.go:69 4 in gvisor.dev/gvisor/pkg/sentry/socket/unix.(*SocketOperations).RecvMsg at pkg/sentry/socket/unix/unix.go:612 5 in gvisor.dev/gvisor/pkg/sentry/syscalls/linux.recvFrom at pkg/sentry/syscalls/linux/sys_socket.go:885 6 in gvisor.dev/gvisor/pkg/sentry/syscalls/linux.RecvFrom at pkg/sentry/syscalls/linux/sys_socket.go:910 ... The issue is caused by that ErrClosedForReceive returned by unix/transport.queue is turned into nil in unix.(*EndpointReader).ReadToBlocks(): err.ToError() As a result, in unix.(*SocketOperations).RecvMsg(): n == 0 and err == nil We shall differentiate it from another case - no data to read where ErrWouldBlock shall be returned; and return 0 immediately. Fixes: #734 Reported-by: chenglang.hy <chenglang.hy@antfin.com> Signed-off-by: Jianfeng Tan <henry.tjf@antfin.com>
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@ -595,7 +595,8 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
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total += n
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}
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if err != nil || !waitAll || isPacket || n >= dst.NumBytes() {
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streamPeerClosed := s.stype == linux.SOCK_STREAM && n == 0 && err == nil
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if err != nil || !waitAll || isPacket || n >= dst.NumBytes() || streamPeerClosed {
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if total > 0 {
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err = nil
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}
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@ -44,6 +44,32 @@ TEST_P(StreamUnixSocketPairTest, ReadOneSideClosed) {
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SyscallSucceedsWithValue(0));
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}
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TEST_P(StreamUnixSocketPairTest, RecvmsgOneSideClosed) {
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auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
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// Set timeout so that it will not wait for ever.
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struct timeval tv {
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.tv_sec = 0, .tv_usec = 10
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};
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EXPECT_THAT(
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setsockopt(sockets->second_fd(), SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)),
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SyscallSucceeds());
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ASSERT_THAT(close(sockets->release_first_fd()), SyscallSucceeds());
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char received_data[10] = {};
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struct iovec iov;
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iov.iov_base = received_data;
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iov.iov_len = sizeof(received_data);
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struct msghdr msg = {};
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msg.msg_flags = -1;
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msg.msg_iov = &iov;
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msg.msg_iovlen = 1;
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ASSERT_THAT(recvmsg(sockets->second_fd(), &msg, MSG_WAITALL),
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SyscallSucceedsWithValue(0));
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}
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INSTANTIATE_TEST_SUITE_P(
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AllUnixDomainSockets, StreamUnixSocketPairTest,
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::testing::ValuesIn(IncludeReversals(VecCat<SocketPairKind>(
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