Implement fallocate(2)

Closes #225

PiperOrigin-RevId: 247508791
Change-Id: I04f47cf2770b30043e5a272aba4ba6e11d0476cc

2 files changed, 20 insertions, 2 deletions

diff --git a/runsc/fsgofer/filter/config.go b/runsc/fsgofer/filter/config.go
index a1ad49fb2..4faab2946 100644
--- a/runsc/fsgofer/filter/config.go
+++ b/runsc/fsgofer/filter/config.go
@@ -62,8 +62,14 @@ var allowedSyscalls = seccomp.SyscallRules{
 	},
 	syscall.SYS_EXIT:       {},
 	syscall.SYS_EXIT_GROUP: {},
-	syscall.SYS_FCHMOD:     {},
-	syscall.SYS_FCHOWNAT:   {},
+	syscall.SYS_FALLOCATE: []seccomp.Rule{
+		{
+			seccomp.AllowAny{},
+			seccomp.AllowValue(0),
+		},
+	},
+	syscall.SYS_FCHMOD:   {},
+	syscall.SYS_FCHOWNAT: {},
 	syscall.SYS_FCNTL: []seccomp.Rule{
 		{
 			seccomp.AllowAny{},
diff --git a/runsc/fsgofer/fsgofer.go b/runsc/fsgofer/fsgofer.go
index 3a0806837..b185015b6 100644
--- a/runsc/fsgofer/fsgofer.go
+++ b/runsc/fsgofer/fsgofer.go
@@ -731,6 +731,18 @@ func (l *localFile) SetAttr(valid p9.SetAttrMask, attr p9.SetAttr) error {
 	return err
 }
 
+// Allocate implements p9.File.
+func (l *localFile) Allocate(mode p9.AllocateMode, offset, length uint64) error {
+	if !l.isOpen() {
+		return syscall.EBADF
+	}
+
+	if err := syscall.Fallocate(l.file.FD(), mode.ToLinux(), int64(offset), int64(length)); err != nil {
+		return extractErrno(err)
+	}
+	return nil
+}
+
 // Rename implements p9.File; this should never be called.
 func (l *localFile) Rename(p9.File, string) error {
 	panic("rename called directly")