From 0b569b7caebc2b7785732ed6cb8248cf0568783f Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Mon, 21 Oct 2019 14:53:44 -0700 Subject: Add basic implementation of execveat syscall and associated tests. Allow file descriptors of directories as well as AT_FDCWD. PiperOrigin-RevId: 275929668 --- pkg/sentry/syscalls/linux/linux64_amd64.go | 2 +- pkg/sentry/syscalls/linux/sys_thread.go | 48 +++++++++++++++++++++++++++--- 2 files changed, 45 insertions(+), 5 deletions(-) (limited to 'pkg/sentry/syscalls/linux') diff --git a/pkg/sentry/syscalls/linux/linux64_amd64.go b/pkg/sentry/syscalls/linux/linux64_amd64.go index e215ac049..9c9ab438e 100644 --- a/pkg/sentry/syscalls/linux/linux64_amd64.go +++ b/pkg/sentry/syscalls/linux/linux64_amd64.go @@ -362,7 +362,7 @@ var AMD64 = &kernel.SyscallTable{ 319: syscalls.Supported("memfd_create", MemfdCreate), 320: syscalls.CapError("kexec_file_load", linux.CAP_SYS_BOOT, "", nil), 321: syscalls.CapError("bpf", linux.CAP_SYS_ADMIN, "", nil), - 322: syscalls.ErrorWithEvent("execveat", syserror.ENOSYS, "", []string{"gvisor.dev/issue/265"}), // TODO(b/118901836) + 322: syscalls.PartiallySupported("execveat", Execveat, "No support for AT_EMPTY_PATH, AT_SYMLINK_FOLLOW.", nil), 323: syscalls.ErrorWithEvent("userfaultfd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/266"}), // TODO(b/118906345) 324: syscalls.ErrorWithEvent("membarrier", syserror.ENOSYS, "", []string{"gvisor.dev/issue/267"}), // TODO(b/118904897) 325: syscalls.PartiallySupported("mlock2", Mlock2, "Stub implementation. The sandbox lacks appropriate permissions.", nil), diff --git a/pkg/sentry/syscalls/linux/sys_thread.go b/pkg/sentry/syscalls/linux/sys_thread.go index 8ab7ffa25..6e425f1ec 100644 --- a/pkg/sentry/syscalls/linux/sys_thread.go +++ b/pkg/sentry/syscalls/linux/sys_thread.go @@ -15,10 +15,12 @@ package linux import ( + "path" "syscall" "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/sentry/arch" + "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/sentry/kernel" "gvisor.dev/gvisor/pkg/sentry/kernel/sched" "gvisor.dev/gvisor/pkg/sentry/usermem" @@ -67,8 +69,22 @@ func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal argvAddr := args[1].Pointer() envvAddr := args[2].Pointer() - // Extract our arguments. - filename, err := t.CopyInString(filenameAddr, linux.PATH_MAX) + return execveat(t, linux.AT_FDCWD, filenameAddr, argvAddr, envvAddr, 0) +} + +// Execveat implements linux syscall execveat(2). +func Execveat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { + dirFD := args[0].Int() + pathnameAddr := args[1].Pointer() + argvAddr := args[2].Pointer() + envvAddr := args[3].Pointer() + flags := args[4].Int() + + return execveat(t, dirFD, pathnameAddr, argvAddr, envvAddr, flags) +} + +func execveat(t *kernel.Task, dirFD int32, pathnameAddr, argvAddr, envvAddr usermem.Addr, flags int32) (uintptr, *kernel.SyscallControl, error) { + pathname, err := t.CopyInString(pathnameAddr, linux.PATH_MAX) if err != nil { return 0, nil, err } @@ -89,14 +105,38 @@ func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal } } + if flags != 0 { + // TODO(b/128449944): Handle AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW. + t.Kernel().EmitUnimplementedEvent(t) + return 0, nil, syserror.ENOSYS + } + root := t.FSContext().RootDirectory() defer root.DecRef() - wd := t.FSContext().WorkingDirectory() + + var wd *fs.Dirent + if dirFD == linux.AT_FDCWD || path.IsAbs(pathname) { + // If pathname is absolute, LoadTaskImage() will ignore the wd. + wd = t.FSContext().WorkingDirectory() + } else { + // Need to extract the given FD. + f := t.GetFile(dirFD) + if f == nil { + return 0, nil, syserror.EBADF + } + defer f.DecRef() + + wd = f.Dirent + wd.IncRef() + if !fs.IsDir(wd.Inode.StableAttr) { + return 0, nil, syserror.ENOTDIR + } + } defer wd.DecRef() // Load the new TaskContext. maxTraversals := uint(linux.MaxSymlinkTraversals) - tc, se := t.Kernel().LoadTaskImage(t, t.MountNamespace(), root, wd, &maxTraversals, filename, nil, argv, envv, t.Arch().FeatureSet()) + tc, se := t.Kernel().LoadTaskImage(t, t.MountNamespace(), root, wd, &maxTraversals, pathname, nil, argv, envv, t.Arch().FeatureSet()) if se != nil { return 0, nil, se.ToError() } -- cgit v1.2.3