Combine executable lookup code

Run vs. exec, VFS1 vs. VFS2 were executable lookup were
slightly different from each other. Combine them all
into the same logic.

PiperOrigin-RevId: 315426443

4 files changed, 54 insertions, 92 deletions

diff --git a/pkg/sentry/control/BUILD b/pkg/sentry/control/BUILD
index 0c9a62f0d..2c5d14be5 100644
--- a/pkg/sentry/control/BUILD
+++ b/pkg/sentry/control/BUILD
@@ -16,15 +16,12 @@ go_library(
     ],
     deps = [
         "//pkg/abi/linux",
-        "//pkg/context",
         "//pkg/fd",
-        "//pkg/fspath",
         "//pkg/log",
         "//pkg/sentry/fdimport",
         "//pkg/sentry/fs",
         "//pkg/sentry/fs/host",
         "//pkg/sentry/fs/user",
-        "//pkg/sentry/fsbridge",
         "//pkg/sentry/fsimpl/host",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
@@ -36,7 +33,6 @@ go_library(
         "//pkg/sentry/vfs",
         "//pkg/sentry/watchdog",
         "//pkg/sync",
-        "//pkg/syserror",
         "//pkg/tcpip/link/sniffer",
         "//pkg/urpc",
         "@org_golang_x_sys//unix:go_default_library",
diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go
index 8767430b7..1bae7cfaf 100644
--- a/pkg/sentry/control/proc.go
+++ b/pkg/sentry/control/proc.go
@@ -25,13 +25,10 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/fdimport"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
 	"gvisor.dev/gvisor/pkg/sentry/fs/user"
-	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
@@ -39,7 +36,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/urpc"
 )
 
@@ -107,6 +103,9 @@ type ExecArgs struct {
 
 // String prints the arguments as a string.
 func (args ExecArgs) String() string {
+	if len(args.Argv) == 0 {
+		return args.Filename
+	}
 	a := make([]string, len(args.Argv))
 	copy(a, args.Argv)
 	if args.Filename != "" {
@@ -179,37 +178,30 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 	}
 	ctx := initArgs.NewContext(proc.Kernel)
 
-	if initArgs.Filename == "" {
-		if kernel.VFS2Enabled {
-			// Get the full path to the filename from the PATH env variable.
-			if initArgs.MountNamespaceVFS2 == nil {
-				// Set initArgs so that 'ctx' returns the namespace.
-				//
-				// MountNamespaceVFS2 adds a reference to the namespace, which is
-				// transferred to the new process.
-				initArgs.MountNamespaceVFS2 = proc.Kernel.GlobalInit().Leader().MountNamespaceVFS2()
-			}
-			file, err := getExecutableFD(ctx, creds, proc.Kernel.VFS(), initArgs.MountNamespaceVFS2, initArgs.Envv, initArgs.WorkingDirectory, initArgs.Argv[0])
-			if err != nil {
-				return nil, 0, nil, nil, fmt.Errorf("error finding executable %q in environment %v: %v", initArgs.Argv[0], initArgs.Envv, err)
-			}
-			initArgs.File = fsbridge.NewVFSFile(file)
-		} else {
-			if initArgs.MountNamespace == nil {
-				// Set initArgs so that 'ctx' returns the namespace.
-				initArgs.MountNamespace = proc.Kernel.GlobalInit().Leader().MountNamespace()
+	if kernel.VFS2Enabled {
+		// Get the full path to the filename from the PATH env variable.
+		if initArgs.MountNamespaceVFS2 == nil {
+			// Set initArgs so that 'ctx' returns the namespace.
+			//
+			// MountNamespaceVFS2 adds a reference to the namespace, which is
+			// transferred to the new process.
+			initArgs.MountNamespaceVFS2 = proc.Kernel.GlobalInit().Leader().MountNamespaceVFS2()
+		}
+	} else {
+		if initArgs.MountNamespace == nil {
+			// Set initArgs so that 'ctx' returns the namespace.
+			initArgs.MountNamespace = proc.Kernel.GlobalInit().Leader().MountNamespace()
 
-				// initArgs must hold a reference on MountNamespace, which will
-				// be donated to the new process in CreateProcess.
-				initArgs.MountNamespace.IncRef()
-			}
-			f, err := user.ResolveExecutablePath(ctx, creds, initArgs.MountNamespace, initArgs.Envv, initArgs.WorkingDirectory, initArgs.Argv[0])
-			if err != nil {
-				return nil, 0, nil, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], initArgs.Envv, err)
-			}
-			initArgs.Filename = f
+			// initArgs must hold a reference on MountNamespace, which will
+			// be donated to the new process in CreateProcess.
+			initArgs.MountNamespace.IncRef()
 		}
 	}
+	resolved, err := user.ResolveExecutablePath(ctx, &initArgs)
+	if err != nil {
+		return nil, 0, nil, nil, err
+	}
+	initArgs.Filename = resolved
 
 	fds := make([]int, len(args.FilePayload.Files))
 	for i, file := range args.FilePayload.Files {
@@ -422,31 +414,3 @@ func ttyName(tty *kernel.TTY) string {
 	}
 	return fmt.Sprintf("pts/%d", tty.Index)
 }
-
-// getExecutableFD resolves the given executable name and returns a
-// vfs.FileDescription for the executable file.
-func getExecutableFD(ctx context.Context, creds *auth.Credentials, vfsObj *vfs.VirtualFilesystem, mns *vfs.MountNamespace, envv []string, wd, name string) (*vfs.FileDescription, error) {
-	path, err := user.ResolveExecutablePathVFS2(ctx, creds, mns, envv, wd, name)
-	if err != nil {
-		return nil, err
-	}
-
-	root := vfs.RootFromContext(ctx)
-	defer root.DecRef()
-
-	pop := vfs.PathOperation{
-		Root:               root,
-		Start:              root, // binPath is absolute, Start can be anything.
-		Path:               fspath.Parse(path),
-		FollowFinalSymlink: true,
-	}
-	opts := &vfs.OpenOptions{
-		Flags:    linux.O_RDONLY,
-		FileExec: true,
-	}
-	f, err := vfsObj.OpenAt(ctx, creds, &pop, opts)
-	if err == syserror.ENOENT || err == syserror.EACCES {
-		return nil, nil
-	}
-	return f, err
-}
diff --git a/pkg/sentry/fs/user/BUILD b/pkg/sentry/fs/user/BUILD
index bd5dac373..66e949c95 100644
--- a/pkg/sentry/fs/user/BUILD
+++ b/pkg/sentry/fs/user/BUILD
@@ -15,6 +15,7 @@ go_library(
         "//pkg/fspath",
         "//pkg/log",
         "//pkg/sentry/fs",
+        "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/vfs",
         "//pkg/syserror",
diff --git a/pkg/sentry/fs/user/path.go b/pkg/sentry/fs/user/path.go
index fbd4547a7..397e96045 100644
--- a/pkg/sentry/fs/user/path.go
+++ b/pkg/sentry/fs/user/path.go
@@ -24,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -31,7 +32,15 @@ import (
 
 // ResolveExecutablePath resolves the given executable name given the working
 // dir and environment.
-func ResolveExecutablePath(ctx context.Context, creds *auth.Credentials, mns *fs.MountNamespace, envv []string, wd, name string) (string, error) {
+func ResolveExecutablePath(ctx context.Context, args *kernel.CreateProcessArgs) (string, error) {
+	name := args.Filename
+	if len(name) == 0 {
+		if len(args.Argv) == 0 {
+			return "", fmt.Errorf("no filename or command provided")
+		}
+		name = args.Argv[0]
+	}
+
 	// Absolute paths can be used directly.
 	if path.IsAbs(name) {
 		return name, nil
@@ -40,6 +49,7 @@ func ResolveExecutablePath(ctx context.Context, creds *auth.Credentials, mns *fs
 	// Paths with '/' in them should be joined to the working directory, or
 	// to the root if working directory is not set.
 	if strings.IndexByte(name, '/') > 0 {
+		wd := args.WorkingDirectory
 		if wd == "" {
 			wd = "/"
 		}
@@ -49,10 +59,24 @@ func ResolveExecutablePath(ctx context.Context, creds *auth.Credentials, mns *fs
 		return path.Join(wd, name), nil
 	}
 
-	// Otherwise, We must lookup the name in the paths, starting from the
-	// calling context's root directory.
-	paths := getPath(envv)
+	// Otherwise, We must lookup the name in the paths.
+	paths := getPath(args.Envv)
+	if kernel.VFS2Enabled {
+		f, err := resolveVFS2(ctx, args.Credentials, args.MountNamespaceVFS2, paths, name)
+		if err != nil {
+			return "", fmt.Errorf("error finding executable %q in PATH %v: %v", name, paths, err)
+		}
+		return f, nil
+	}
+
+	f, err := resolve(ctx, args.MountNamespace, paths, name)
+	if err != nil {
+		return "", fmt.Errorf("error finding executable %q in PATH %v: %v", name, paths, err)
+	}
+	return f, nil
+}
 
+func resolve(ctx context.Context, mns *fs.MountNamespace, paths []string, name string) (string, error) {
 	root := fs.RootFromContext(ctx)
 	if root == nil {
 		// Caller has no root. Don't bother traversing anything.
@@ -95,30 +119,7 @@ func ResolveExecutablePath(ctx context.Context, creds *auth.Credentials, mns *fs
 	return "", syserror.ENOENT
 }
 
-// ResolveExecutablePathVFS2 resolves the given executable name given the
-// working dir and environment.
-func ResolveExecutablePathVFS2(ctx context.Context, creds *auth.Credentials, mns *vfs.MountNamespace, envv []string, wd, name string) (string, error) {
-	// Absolute paths can be used directly.
-	if path.IsAbs(name) {
-		return name, nil
-	}
-
-	// Paths with '/' in them should be joined to the working directory, or
-	// to the root if working directory is not set.
-	if strings.IndexByte(name, '/') > 0 {
-		if wd == "" {
-			wd = "/"
-		}
-		if !path.IsAbs(wd) {
-			return "", fmt.Errorf("working directory %q must be absolute", wd)
-		}
-		return path.Join(wd, name), nil
-	}
-
-	// Otherwise, We must lookup the name in the paths, starting from the
-	// calling context's root directory.
-	paths := getPath(envv)
-
+func resolveVFS2(ctx context.Context, creds *auth.Credentials, mns *vfs.MountNamespace, paths []string, name string) (string, error) {
 	root := mns.Root()
 	defer root.DecRef()
 	for _, p := range paths {