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unix: return zero if peer is closed

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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>
This commit is contained in:
Jianfeng Tan
2019-08-22 15:25:38 +00:00
parent 8d9276ed56
commit 96f78e2466
2 changed files with 28 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/socket/unix/unix.go
+2 -1
View File
@@ -595,7 +595,8 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
total += n
}
if err != nil || !waitAll || isPacket || n >= dst.NumBytes() {
streamPeerClosed := s.stype == linux.SOCK_STREAM && n == 0 && err == nil
if err != nil || !waitAll || isPacket || n >= dst.NumBytes() || streamPeerClosed {
if total > 0 {
err = nil
}
test/syscalls/linux/socket_unix_stream.cc
+26
View File
@@ -44,6 +44,32 @@ TEST_P(StreamUnixSocketPairTest, ReadOneSideClosed) {
SyscallSucceedsWithValue(0));
}
TEST_P(StreamUnixSocketPairTest, RecvmsgOneSideClosed) {
auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
// Set timeout so that it will not wait for ever.
struct timeval tv {
.tv_sec = 0, .tv_usec = 10
};
EXPECT_THAT(
setsockopt(sockets->second_fd(), SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)),
SyscallSucceeds());
ASSERT_THAT(close(sockets->release_first_fd()), SyscallSucceeds());
char received_data[10] = {};
struct iovec iov;
iov.iov_base = received_data;
iov.iov_len = sizeof(received_data);
struct msghdr msg = {};
msg.msg_flags = -1;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
ASSERT_THAT(recvmsg(sockets->second_fd(), &msg, MSG_WAITALL),
SyscallSucceedsWithValue(0));
}
INSTANTIATE_TEST_SUITE_P(
AllUnixDomainSockets, StreamUnixSocketPairTest,
::testing::ValuesIn(IncludeReversals(VecCat<SocketPairKind>(