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Save shutdown flags first.

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With rpcinet if shutdown flags are not saved before making
the rpc a race is possible where blocked threads are woken
up before the flags have been persisted. This would mean
that threads can block indefinitely in a recvmsg after a
shutdown(SHUT_RD) has happened.

PiperOrigin-RevId: 223089783
Change-Id: If595e7add12aece54bcdf668ab64c570910d061a
This commit is contained in:
Brian Geffon
2018-11-27 17:48:05 -08:00
committed by Shentubot
parent 9e0f132377
commit 5bd02b224f
1 changed files with 7 additions and 4 deletions
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pkg/sentry/socket/rpcinet/socket.go
+7 -4
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@@ -354,6 +354,13 @@ func (s *socketOperations) Listen(t *kernel.Task, backlog int) *syserr.Error {
// Shutdown implements socket.Socket.Shutdown.
func (s *socketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
// We save the shutdown state because of strange differences on linux
// related to recvs on blocking vs. non-blocking sockets after a SHUT_RD.
// We need to emulate that behavior on the blocking side.
// TODO: There is a possible race that can exist with loopback,
// where data could possibly be lost.
s.setShutdownFlags(how)
stack := t.NetworkContext().(*Stack)
id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Shutdown{&pb.ShutdownRequest{Fd: s.fd, How: int64(how)}}}, false /* ignoreResult */)
<-c
@@ -362,10 +369,6 @@ func (s *socketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
return syserr.FromHost(syscall.Errno(e))
}
// We save the shutdown state because of strange differences on linux
// related to recvs on blocking vs. non-blocking sockets after a SHUT_RD.
// We need to emulate that behavior on the blocking side.
s.setShutdownFlags(how)
return nil
}