From 1c480abc39b9957606ff8bf125a5c253ad8a76cb Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Fri, 25 Oct 2019 22:31:35 -0700 Subject: Aggregate arguments for loading executables into a single struct. This change simplifies the function signatures of functions related to loading executables, such as LoadTaskImage, Load, loadBinary. PiperOrigin-RevId: 276821187 --- pkg/sentry/kernel/kernel.go | 14 +++- pkg/sentry/kernel/task_context.go | 27 ++----- pkg/sentry/loader/elf.go | 17 ++-- pkg/sentry/loader/loader.go | 132 +++++++++++++++++++++----------- pkg/sentry/syscalls/linux/BUILD | 1 + pkg/sentry/syscalls/linux/sys_thread.go | 18 ++++- 6 files changed, 136 insertions(+), 73 deletions(-) diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go index d70ad5c09..fcfe7a16d 100644 --- a/pkg/sentry/kernel/kernel.go +++ b/pkg/sentry/kernel/kernel.go @@ -804,8 +804,20 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID, // Create a fresh task context. remainingTraversals = uint(args.MaxSymlinkTraversals) + loadArgs := loader.LoadArgs{ + Mounts: mounts, + Root: root, + WorkingDirectory: wd, + RemainingTraversals: &remainingTraversals, + ResolveFinal: true, + Filename: args.Filename, + File: args.File, + Argv: args.Argv, + Envv: args.Envv, + Features: k.featureSet, + } - tc, se := k.LoadTaskImage(ctx, mounts, root, wd, &remainingTraversals, args.Filename, args.File, args.Argv, args.Envv, true /*resolveFinal*/, k.featureSet) + tc, se := k.LoadTaskImage(ctx, loadArgs) if se != nil { return nil, 0, errors.New(se.String()) } diff --git a/pkg/sentry/kernel/task_context.go b/pkg/sentry/kernel/task_context.go index 1da718b27..bb5560acf 100644 --- a/pkg/sentry/kernel/task_context.go +++ b/pkg/sentry/kernel/task_context.go @@ -18,10 +18,8 @@ import ( "fmt" "gvisor.dev/gvisor/pkg/abi/linux" - "gvisor.dev/gvisor/pkg/cpuid" "gvisor.dev/gvisor/pkg/sentry/arch" "gvisor.dev/gvisor/pkg/sentry/context" - "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/sentry/kernel/futex" "gvisor.dev/gvisor/pkg/sentry/loader" "gvisor.dev/gvisor/pkg/sentry/mm" @@ -132,30 +130,21 @@ func (t *Task) Stack() *arch.Stack { return &arch.Stack{t.Arch(), t.MemoryManager(), usermem.Addr(t.Arch().Stack())} } -// LoadTaskImage loads filename into a new TaskContext. +// LoadTaskImage loads a specified file into a new TaskContext. // -// It takes several arguments: -// * mounts: MountNamespace to lookup filename in -// * root: Root to lookup filename under -// * wd: Working directory to lookup filename under -// * maxTraversals: maximum number of symlinks to follow -// * filename: path to binary to load -// * file: an open fs.File object of the binary to load. If set, -// file will be loaded and not filename. -// * argv: Binary argv -// * envv: Binary envv -// * fs: Binary FeatureSet -func (k *Kernel) LoadTaskImage(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, filename string, file *fs.File, argv, envv []string, resolveFinal bool, fs *cpuid.FeatureSet) (*TaskContext, *syserr.Error) { - // If File is not nil, we should load that instead of resolving filename. - if file != nil { - filename = file.MappedName(ctx) +// args.MemoryManager does not need to be set by the caller. +func (k *Kernel) LoadTaskImage(ctx context.Context, args loader.LoadArgs) (*TaskContext, *syserr.Error) { + // If File is not nil, we should load that instead of resolving Filename. + if args.File != nil { + args.Filename = args.File.MappedName(ctx) } // Prepare a new user address space to load into. m := mm.NewMemoryManager(k, k) defer m.DecUsers(ctx) + args.MemoryManager = m - os, ac, name, err := loader.Load(ctx, m, mounts, root, wd, maxTraversals, fs, filename, file, argv, envv, resolveFinal, k.extraAuxv, k.vdso) + os, ac, name, err := loader.Load(ctx, args, k.extraAuxv, k.vdso) if err != nil { return nil, err } diff --git a/pkg/sentry/loader/elf.go b/pkg/sentry/loader/elf.go index 86f6b269b..3ea037e4d 100644 --- a/pkg/sentry/loader/elf.go +++ b/pkg/sentry/loader/elf.go @@ -624,15 +624,15 @@ func loadInterpreterELF(ctx context.Context, m *mm.MemoryManager, f *fs.File, in return loadParsedELF(ctx, m, f, info, 0) } -// loadELF loads f into the Task address space. +// loadELF loads args.File into the Task address space. // // If loadELF returns ErrSwitchFile it should be called again with the returned // path and argv. // // Preconditions: -// * f is an ELF file -func loadELF(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, fs *cpuid.FeatureSet, f *fs.File) (loadedELF, arch.Context, error) { - bin, ac, err := loadInitialELF(ctx, m, fs, f) +// * args.File is an ELF file +func loadELF(ctx context.Context, args LoadArgs) (loadedELF, arch.Context, error) { + bin, ac, err := loadInitialELF(ctx, args.MemoryManager, args.Features, args.File) if err != nil { ctx.Infof("Error loading binary: %v", err) return loadedELF{}, nil, err @@ -640,7 +640,12 @@ func loadELF(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace var interp loadedELF if bin.interpreter != "" { - d, i, err := openPath(ctx, mounts, root, wd, maxTraversals, bin.interpreter, true /*resolveFinal*/) + // Even if we do not allow the final link of the script to be + // resolved, the interpreter should still be resolved if it is + // a symlink. + args.ResolveFinal = true + args.Filename = bin.interpreter + d, i, err := openPath(ctx, args) if err != nil { ctx.Infof("Error opening interpreter %s: %v", bin.interpreter, err) return loadedELF{}, nil, err @@ -649,7 +654,7 @@ func loadELF(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace // We don't need the Dirent. d.DecRef() - interp, err = loadInterpreterELF(ctx, m, i, bin) + interp, err = loadInterpreterELF(ctx, args.MemoryManager, i, bin) if err != nil { ctx.Infof("Error loading interpreter: %v", err) return loadedELF{}, nil, err diff --git a/pkg/sentry/loader/loader.go b/pkg/sentry/loader/loader.go index f5303491d..818941762 100644 --- a/pkg/sentry/loader/loader.go +++ b/pkg/sentry/loader/loader.go @@ -12,7 +12,7 @@ // See the License for the specific language governing permissions and // limitations under the License. -// Package loader loads a binary into a MemoryManager. +// Package loader loads an executable file into a MemoryManager. package loader import ( @@ -35,6 +35,48 @@ import ( "gvisor.dev/gvisor/pkg/syserror" ) +// LoadArgs holds specifications for an executable file to be loaded. +type LoadArgs struct { + // MemoryManager is the memory manager to load the executable into. + MemoryManager *mm.MemoryManager + + // Mounts is the mount namespace in which to look up Filename. + Mounts *fs.MountNamespace + + // Root is the root directory under which to look up Filename. + Root *fs.Dirent + + // WorkingDirectory is the working directory under which to look up + // Filename. + WorkingDirectory *fs.Dirent + + // RemainingTraversals is the maximum number of symlinks to follow to + // resolve Filename. This counter is passed by reference to keep it + // updated throughout the call stack. + RemainingTraversals *uint + + // ResolveFinal indicates whether the final link of Filename should be + // resolved, if it is a symlink. + ResolveFinal bool + + // Filename is the path for the executable. + Filename string + + // File is an open fs.File object of the executable. If File is not + // nil, then File will be loaded and Filename will be ignored. + File *fs.File + + // Argv is the vector of arguments to pass to the executable. + Argv []string + + // Envv is the vector of environment variables to pass to the + // executable. + Envv []string + + // Features specifies the CPU feature set for the executable. + Features *cpuid.FeatureSet +} + // readFull behaves like io.ReadFull for an *fs.File. func readFull(ctx context.Context, f *fs.File, dst usermem.IOSequence, offset int64) (int64, error) { var total int64 @@ -51,24 +93,24 @@ func readFull(ctx context.Context, f *fs.File, dst usermem.IOSequence, offset in return total, nil } -// openPath opens name for loading. +// openPath opens args.Filename for loading. // -// openPath returns the fs.Dirent and an *fs.File for name, which is not -// installed in the Task FDTable. The caller takes ownership of both. +// openPath returns the fs.Dirent and an *fs.File for args.Filename, which is +// not installed in the Task FDTable. The caller takes ownership of both. // -// name must be a readable, executable, regular file. -func openPath(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, name string, resolveFinal bool) (*fs.Dirent, *fs.File, error) { +// args.Filename must be a readable, executable, regular file. +func openPath(ctx context.Context, args LoadArgs) (*fs.Dirent, *fs.File, error) { var err error - if name == "" { + if args.Filename == "" { ctx.Infof("cannot open empty name") return nil, nil, syserror.ENOENT } var d *fs.Dirent - if resolveFinal { - d, err = mounts.FindInode(ctx, root, wd, name, maxTraversals) + if args.ResolveFinal { + d, err = args.Mounts.FindInode(ctx, args.Root, args.WorkingDirectory, args.Filename, args.RemainingTraversals) } else { - d, err = mounts.FindLink(ctx, root, wd, name, maxTraversals) + d, err = args.Mounts.FindLink(ctx, args.Root, args.WorkingDirectory, args.Filename, args.RemainingTraversals) } if err != nil { return nil, nil, err @@ -77,11 +119,11 @@ func openPath(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Diren // Open file will take a reference to Dirent, so destroy this one. defer d.DecRef() - if !resolveFinal && fs.IsSymlink(d.Inode.StableAttr) { + if !args.ResolveFinal && fs.IsSymlink(d.Inode.StableAttr) { return nil, nil, syserror.ELOOP } - return openFile(ctx, nil, d, name) + return openFile(ctx, nil, d, args.Filename) } // openFile takes that file's Dirent and performs checks on it. If provided a @@ -182,34 +224,33 @@ const ( maxLoaderAttempts = 6 ) -// loadBinary loads a binary that is pointed to by "file". If nil, the path -// "filename" is resolved and loaded. +// loadExecutable loads an executable that is pointed to by args.File. If nil, +// the path args.Filename is resolved and loaded. If the executable is an +// interpreter script rather than an ELF, the binary of the corresponding +// interpreter will be loaded. // // It returns: // * loadedELF, description of the loaded binary // * arch.Context matching the binary arch // * fs.Dirent of the binary file -// * Possibly updated argv -func loadBinary(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, root, wd *fs.Dirent, remainingTraversals *uint, features *cpuid.FeatureSet, filename string, passedFile *fs.File, argv []string, resolveFinal bool) (loadedELF, arch.Context, *fs.Dirent, []string, error) { +// * Possibly updated args.Argv +func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context, *fs.Dirent, []string, error) { for i := 0; i < maxLoaderAttempts; i++ { var ( d *fs.Dirent - f *fs.File err error ) - if passedFile == nil { - d, f, err = openPath(ctx, mounts, root, wd, remainingTraversals, filename, resolveFinal) + if args.File == nil { + d, args.File, err = openPath(ctx, args) } else { - d, f, err = openFile(ctx, passedFile, nil, "") - // Set to nil in case we loop on a Interpreter Script. - passedFile = nil + d, args.File, err = openFile(ctx, args.File, nil, "") } if err != nil { - ctx.Infof("Error opening %s: %v", filename, err) + ctx.Infof("Error opening %s: %v", args.Filename, err) return loadedELF{}, nil, nil, nil, err } - defer f.DecRef() + defer args.File.DecRef() // We will return d in the successful case, but defer a DecRef // for intermediate loops and failure cases. defer d.DecRef() @@ -217,9 +258,9 @@ func loadBinary(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamesp // Check the header. Is this an ELF or interpreter script? var hdr [4]uint8 // N.B. We assume that reading from a regular file cannot block. - _, err = readFull(ctx, f, usermem.BytesIOSequence(hdr[:]), 0) - // Allow unexpected EOF, as a valid executable could be only three - // bytes (e.g., #!a). + _, err = readFull(ctx, args.File, usermem.BytesIOSequence(hdr[:]), 0) + // Allow unexpected EOF, as a valid executable could be only + // three bytes (e.g., #!a). if err != nil && err != io.ErrUnexpectedEOF { if err == io.EOF { err = syserror.ENOEXEC @@ -229,33 +270,33 @@ func loadBinary(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamesp switch { case bytes.Equal(hdr[:], []byte(elfMagic)): - loaded, ac, err := loadELF(ctx, m, mounts, root, wd, remainingTraversals, features, f) + loaded, ac, err := loadELF(ctx, args) if err != nil { ctx.Infof("Error loading ELF: %v", err) return loadedELF{}, nil, nil, nil, err } // An ELF is always terminal. Hold on to d. d.IncRef() - return loaded, ac, d, argv, err + return loaded, ac, d, args.Argv, err case bytes.Equal(hdr[:2], []byte(interpreterScriptMagic)): - newpath, newargv, err := parseInterpreterScript(ctx, filename, f, argv) + args.Filename, args.Argv, err = parseInterpreterScript(ctx, args.Filename, args.File, args.Argv) if err != nil { ctx.Infof("Error loading interpreter script: %v", err) return loadedELF{}, nil, nil, nil, err } - filename = newpath - argv = newargv default: ctx.Infof("Unknown magic: %v", hdr) return loadedELF{}, nil, nil, nil, syserror.ENOEXEC } + // Set to nil in case we loop on a Interpreter Script. + args.File = nil } return loadedELF{}, nil, nil, nil, syserror.ELOOP } -// Load loads "file" into a MemoryManager. If file is nil, the path "filename" -// is resolved and loaded instead. +// Load loads args.File into a MemoryManager. If args.File is nil, the path +// args.Filename is resolved and loaded instead. // // If Load returns ErrSwitchFile it should be called again with the returned // path and argv. @@ -263,37 +304,37 @@ func loadBinary(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamesp // Preconditions: // * The Task MemoryManager is empty. // * Load is called on the Task goroutine. -func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, fs *cpuid.FeatureSet, filename string, file *fs.File, argv, envv []string, resolveFinal bool, extraAuxv []arch.AuxEntry, vdso *VDSO) (abi.OS, arch.Context, string, *syserr.Error) { - // Load the binary itself. - loaded, ac, d, argv, err := loadBinary(ctx, m, mounts, root, wd, maxTraversals, fs, filename, file, argv, resolveFinal) +func Load(ctx context.Context, args LoadArgs, extraAuxv []arch.AuxEntry, vdso *VDSO) (abi.OS, arch.Context, string, *syserr.Error) { + // Load the executable itself. + loaded, ac, d, newArgv, err := loadExecutable(ctx, args) if err != nil { - return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load %s: %v", filename, err), syserr.FromError(err).ToLinux()) + return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load %s: %v", args.Filename, err), syserr.FromError(err).ToLinux()) } defer d.DecRef() // Load the VDSO. - vdsoAddr, err := loadVDSO(ctx, m, vdso, loaded) + vdsoAddr, err := loadVDSO(ctx, args.MemoryManager, vdso, loaded) if err != nil { return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Error loading VDSO: %v", err), syserr.FromError(err).ToLinux()) } // Setup the heap. brk starts at the next page after the end of the - // binary. Userspace can assume that the remainer of the page after + // executable. Userspace can assume that the remainer of the page after // loaded.end is available for its use. e, ok := loaded.end.RoundUp() if !ok { return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("brk overflows: %#x", loaded.end), linux.ENOEXEC) } - m.BrkSetup(ctx, e) + args.MemoryManager.BrkSetup(ctx, e) // Allocate our stack. - stack, err := allocStack(ctx, m, ac) + stack, err := allocStack(ctx, args.MemoryManager, ac) if err != nil { return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to allocate stack: %v", err), syserr.FromError(err).ToLinux()) } // Push the original filename to the stack, for AT_EXECFN. - execfn, err := stack.Push(filename) + execfn, err := stack.Push(args.Filename) if err != nil { return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to push exec filename: %v", err), syserr.FromError(err).ToLinux()) } @@ -327,11 +368,12 @@ func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, r }...) auxv = append(auxv, extraAuxv...) - sl, err := stack.Load(argv, envv, auxv) + sl, err := stack.Load(newArgv, args.Envv, auxv) if err != nil { return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load stack: %v", err), syserr.FromError(err).ToLinux()) } + m := args.MemoryManager m.SetArgvStart(sl.ArgvStart) m.SetArgvEnd(sl.ArgvEnd) m.SetEnvvStart(sl.EnvvStart) @@ -342,7 +384,7 @@ func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, r ac.SetIP(uintptr(loaded.entry)) ac.SetStack(uintptr(stack.Bottom)) - name := path.Base(filename) + name := path.Base(args.Filename) if len(name) > linux.TASK_COMM_LEN-1 { name = name[:linux.TASK_COMM_LEN-1] } diff --git a/pkg/sentry/syscalls/linux/BUILD b/pkg/sentry/syscalls/linux/BUILD index fb2c1777f..4c0bf96e4 100644 --- a/pkg/sentry/syscalls/linux/BUILD +++ b/pkg/sentry/syscalls/linux/BUILD @@ -79,6 +79,7 @@ go_library( "//pkg/sentry/kernel/signalfd", "//pkg/sentry/kernel/time", "//pkg/sentry/limits", + "//pkg/sentry/loader", "//pkg/sentry/memmap", "//pkg/sentry/mm", "//pkg/sentry/safemem", diff --git a/pkg/sentry/syscalls/linux/sys_thread.go b/pkg/sentry/syscalls/linux/sys_thread.go index effe16186..2476f8858 100644 --- a/pkg/sentry/syscalls/linux/sys_thread.go +++ b/pkg/sentry/syscalls/linux/sys_thread.go @@ -23,6 +23,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/sentry/kernel" "gvisor.dev/gvisor/pkg/sentry/kernel/sched" + "gvisor.dev/gvisor/pkg/sentry/loader" "gvisor.dev/gvisor/pkg/sentry/usermem" "gvisor.dev/gvisor/pkg/syserror" ) @@ -147,8 +148,21 @@ func execveat(t *kernel.Task, dirFD int32, pathnameAddr, argvAddr, envvAddr user } // Load the new TaskContext. - maxTraversals := uint(linux.MaxSymlinkTraversals) - tc, se := t.Kernel().LoadTaskImage(t, t.MountNamespace(), root, wd, &maxTraversals, pathname, executable, argv, envv, resolveFinal, t.Arch().FeatureSet()) + remainingTraversals := uint(linux.MaxSymlinkTraversals) + loadArgs := loader.LoadArgs{ + Mounts: t.MountNamespace(), + Root: root, + WorkingDirectory: wd, + RemainingTraversals: &remainingTraversals, + ResolveFinal: resolveFinal, + Filename: pathname, + File: executable, + Argv: argv, + Envv: envv, + Features: t.Arch().FeatureSet(), + } + + tc, se := t.Kernel().LoadTaskImage(t, loadArgs) if se != nil { return 0, nil, se.ToError() } -- cgit v1.2.3