Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 117 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/error.go b/pkg/sentry/syscalls/linux/error.go
new file mode 100644
index 000000000..013b385bc
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/error.go
@@ -0,0 +1,117 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"io"
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/metric"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+var (
+	partialResultMetric = metric.MustCreateNewUint64Metric("/syscalls/partial_result", true /* sync */, "Whether or not a partial result has occurred for this sandbox.")
+	partialResultOnce   sync.Once
+)
+
+// handleIOError handles special error cases for partial results. For some
+// errors, we may consume the error and return only the partial read/write.
+//
+// op and f are used only for panics.
+func handleIOError(t *kernel.Task, partialResult bool, err, intr error, op string, f *fs.File) error {
+	switch err {
+	case nil:
+		// Typical successful syscall.
+		return nil
+	case io.EOF:
+		// EOF is always consumed. If this is a partial read/write
+		// (result != 0), the application will see that, otherwise
+		// they will see 0.
+		return nil
+	case syserror.ErrExceedsFileSizeLimit:
+		// Ignore partialResult because this error only applies to
+		// normal files, and for those files we cannot accumulate
+		// write results.
+		//
+		// Do not consume the error and return it as EFBIG.
+		// Simultaneously send a SIGXFSZ per setrlimit(2).
+		t.SendSignal(&arch.SignalInfo{
+			Signo: int32(syscall.SIGXFSZ),
+			Code:  arch.SignalInfoKernel,
+		})
+		return syscall.EFBIG
+	case syserror.ErrInterrupted:
+		// The syscall was interrupted. Return nil if it completed
+		// partially, otherwise return the error code that the syscall
+		// needs (to indicate to the kernel what it should do).
+		if partialResult {
+			return nil
+		}
+		return intr
+	}
+
+	if !partialResult {
+		// Typical syscall error.
+		return err
+	}
+
+	switch err {
+	case syserror.EINTR:
+		// Syscall interrupted, but completed a partial
+		// read/write.  Like ErrWouldBlock, since we have a
+		// partial read/write, we consume the error and return
+		// the partial result.
+		return nil
+	case syserror.EFAULT:
+		// EFAULT is only shown the user if nothing was
+		// read/written. If we read something (this case), they see
+		// a partial read/write. They will then presumably try again
+		// with an incremented buffer, which will EFAULT with
+		// result == 0.
+		return nil
+	case syserror.EPIPE:
+		// Writes to a pipe or socket will return EPIPE if the other
+		// side is gone. The partial write is returned. EPIPE will be
+		// returned on the next call.
+		//
+		// TODO: In some cases SIGPIPE should also be sent
+		// to the application.
+		return nil
+	case syserror.ErrWouldBlock:
+		// Syscall would block, but completed a partial read/write.
+		// This case should only be returned by IssueIO for nonblocking
+		// files. Since we have a partial read/write, we consume
+		// ErrWouldBlock, returning the partial result.
+		return nil
+	}
+
+	switch err.(type) {
+	case kernel.SyscallRestartErrno:
+		// Identical to the EINTR case.
+		return nil
+	}
+
+	// An unknown error is encountered with a partial read/write.
+	name, _ := f.Dirent.FullName(nil /* ignore chroot */)
+	log.Traceback("Invalid request partialResult %v and err (type %T) %v for %s operation on %q, %T", partialResult, err, err, op, name, f.FileOperations)
+	partialResultOnce.Do(partialResultMetric.Increment)
+	return nil
+}