7 files changed, 49 insertions, 30 deletions
diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index f4ddfa406..2d43dff1d 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -344,6 +344,10 @@ func (i *Inode) SetTimestamps(ctx context.Context, d *Dirent, ts TimeSpec) error
 
 // Truncate calls i.InodeOperations.Truncate with i as the Inode.
 func (i *Inode) Truncate(ctx context.Context, d *Dirent, size int64) error {
+	if IsDir(i.StableAttr) {
+		return syserror.EISDIR
+	}
+
 	if i.overlay != nil {
 		return overlayTruncate(ctx, i.overlay, d, size)
 	}
diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index 5a388dad1..a09147080 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -462,7 +462,9 @@ func overlayBind(ctx context.Context, o *overlayEntry, parent *Dirent, name stri
 		inode.DecRef()
 		return nil, err
 	}
-	return NewDirent(ctx, newOverlayInode(ctx, entry, inode.MountSource), name), nil
+	// Use the parent's MountSource, since that corresponds to the overlay,
+	// and not the upper filesystem.
+	return NewDirent(ctx, newOverlayInode(ctx, entry, parent.Inode.MountSource), name), nil
 }
 
 func overlayBoundEndpoint(o *overlayEntry, path string) transport.BoundEndpoint {
diff --git a/pkg/sentry/fs/tty/master.go b/pkg/sentry/fs/tty/master.go
index 19b7557d5..bc56be696 100644
--- a/pkg/sentry/fs/tty/master.go
+++ b/pkg/sentry/fs/tty/master.go
@@ -32,6 +32,7 @@ import (
 // +stateify savable
 type masterInodeOperations struct {
 	fsutil.SimpleFileInode
+	fsutil.InodeNoopTruncate
 
 	// d is the containing dir.
 	d *dirInodeOperations
diff --git a/pkg/sentry/fs/tty/slave.go b/pkg/sentry/fs/tty/slave.go
index 944c4ada1..4cbea0367 100644
--- a/pkg/sentry/fs/tty/slave.go
+++ b/pkg/sentry/fs/tty/slave.go
@@ -31,6 +31,7 @@ import (
 // +stateify savable
 type slaveInodeOperations struct {
 	fsutil.SimpleFileInode
+	fsutil.InodeNoopTruncate
 
 	// d is the containing dir.
 	d *dirInodeOperations
diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go
index b9a8e3e21..167c2b60b 100644
--- a/pkg/sentry/syscalls/linux/sys_file.go
+++ b/pkg/sentry/syscalls/linux/sys_file.go
@@ -169,10 +169,11 @@ func openAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint) (fd uint
 			if dirPath {
 				return syserror.ENOTDIR
 			}
-			if flags&linux.O_TRUNC != 0 {
-				if err := d.Inode.Truncate(t, d, 0); err != nil {
-					return err
-				}
+		}
+
+		if flags&linux.O_TRUNC != 0 {
+			if err := d.Inode.Truncate(t, d, 0); err != nil {
+				return err
 			}
 		}
 
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index b5a72ce63..ab1001f16 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -447,16 +447,13 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 		return 0, nil, syserror.ENOTSOCK
 	}
 
-	// Read the length if present. Reject negative values.
+	// Read the length. Reject negative values.
 	optLen := int32(0)
-	if optLenAddr != 0 {
-		if _, err := t.CopyIn(optLenAddr, &optLen); err != nil {
-			return 0, nil, err
-		}
-
-		if optLen < 0 {
-			return 0, nil, syserror.EINVAL
-		}
+	if _, err := t.CopyIn(optLenAddr, &optLen); err != nil {
+		return 0, nil, err
+	}
+	if optLen < 0 {
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Call syscall implementation then copy both value and value len out.
@@ -465,11 +462,9 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 		return 0, nil, e.ToError()
 	}
 
-	if optLenAddr != 0 {
-		vLen := int32(binary.Size(v))
-		if _, err := t.CopyOut(optLenAddr, vLen); err != nil {
-			return 0, nil, err
-		}
+	vLen := int32(binary.Size(v))
+	if _, err := t.CopyOut(optLenAddr, vLen); err != nil {
+		return 0, nil, err
 	}
 
 	if v != nil {
diff --git a/pkg/sentry/usermem/bytes_io.go b/pkg/sentry/usermem/bytes_io.go
index 8d88396ba..7898851b3 100644
--- a/pkg/sentry/usermem/bytes_io.go
+++ b/pkg/sentry/usermem/bytes_io.go
@@ -102,19 +102,34 @@ func (b *BytesIO) rangeCheck(addr Addr, length int) (int, error) {
 }
 
 func (b *BytesIO) blocksFromAddrRanges(ars AddrRangeSeq) (safemem.BlockSeq, error) {
-	blocks := make([]safemem.Block, 0, ars.NumRanges())
-	for !ars.IsEmpty() {
-		ar := ars.Head()
-		n, err := b.rangeCheck(ar.Start, int(ar.Length()))
-		if n != 0 {
-			blocks = append(blocks, safemem.BlockFromSafeSlice(b.Bytes[int(ar.Start):int(ar.Start)+n]))
+	switch ars.NumRanges() {
+	case 0:
+		return safemem.BlockSeq{}, nil
+	case 1:
+		block, err := b.blockFromAddrRange(ars.Head())
+		return safemem.BlockSeqOf(block), err
+	default:
+		blocks := make([]safemem.Block, 0, ars.NumRanges())
+		for !ars.IsEmpty() {
+			block, err := b.blockFromAddrRange(ars.Head())
+			if block.Len() != 0 {
+				blocks = append(blocks, block)
+			}
+			if err != nil {
+				return safemem.BlockSeqFromSlice(blocks), err
+			}
+			ars = ars.Tail()
 		}
-		if err != nil {
-			return safemem.BlockSeqFromSlice(blocks), err
-		}
-		ars = ars.Tail()
+		return safemem.BlockSeqFromSlice(blocks), nil
+	}
+}
+
+func (b *BytesIO) blockFromAddrRange(ar AddrRange) (safemem.Block, error) {
+	n, err := b.rangeCheck(ar.Start, int(ar.Length()))
+	if n == 0 {
+		return safemem.Block{}, err
 	}
-	return safemem.BlockSeqFromSlice(blocks), nil
+	return safemem.BlockFromSafeSlice(b.Bytes[int(ar.Start) : int(ar.Start)+n]), err
 }
 
 // BytesIOSequence returns an IOSequence representing the given byte slice.