diff --git a/frontend/dockerfile/dockerfile2llb/convert.go b/frontend/dockerfile/dockerfile2llb/convert.go
index 756d7e16..7ac992f3 100644
--- a/frontend/dockerfile/dockerfile2llb/convert.go
+++ b/frontend/dockerfile/dockerfile2llb/convert.go
@@ -467,7 +467,11 @@ func dispatchRun(d *dispatchState, c *instructions.RunCommand, proxy *llb.ProxyE
 		opt = append(opt, llb.WithProxy(*proxy))
 	}
 
-	opt = append(opt, dispatchRunMounts(d, c, sources, dopt)...)
+	runMounts, err := dispatchRunMounts(d, c, sources, dopt)
+	if err != nil {
+		return err
+	}
+	opt = append(opt, runMounts...)
 
 	d.state = d.state.Run(opt...).Root()
 	return commitToHistory(&d.image, "RUN "+runCommandString(args, d.buildArgs), true, &d.state)
diff --git a/frontend/dockerfile/dockerfile2llb/convert_norunmount.go b/frontend/dockerfile/dockerfile2llb/convert_norunmount.go
index b358ee68..a4544e79 100644
--- a/frontend/dockerfile/dockerfile2llb/convert_norunmount.go
+++ b/frontend/dockerfile/dockerfile2llb/convert_norunmount.go
@@ -11,6 +11,6 @@ func detectRunMount(cmd *command, dispatchStatesByName map[string]*dispatchState
 	return false
 }
 
-func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*dispatchState, opt dispatchOpt) []llb.RunOption {
-	return nil
+func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*dispatchState, opt dispatchOpt) ([]llb.RunOption, error) {
+	return nil, nil
 }
diff --git a/frontend/dockerfile/dockerfile2llb/convert_runmount.go b/frontend/dockerfile/dockerfile2llb/convert_runmount.go
index 905e1558..61408e1f 100644
--- a/frontend/dockerfile/dockerfile2llb/convert_runmount.go
+++ b/frontend/dockerfile/dockerfile2llb/convert_runmount.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/frontend/dockerfile/instructions"
+	"github.com/pkg/errors"
 )
 
 func detectRunMount(cmd *command, dispatchStatesByName map[string]*dispatchState, allDispatchStates []*dispatchState) bool {
@@ -40,7 +41,7 @@ func detectRunMount(cmd *command, dispatchStatesByName map[string]*dispatchState
 	return false
 }
 
-func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*dispatchState, opt dispatchOpt) []llb.RunOption {
+func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*dispatchState, opt dispatchOpt) ([]llb.RunOption, error) {
 	var out []llb.RunOption
 	mounts := instructions.GetMounts(c)
 
@@ -61,14 +62,25 @@ func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*
 			mountOpts = append(mountOpts, llb.Readonly)
 		}
 		if mount.Type == instructions.MountTypeCache {
-			mountOpts = append(mountOpts, llb.AsPersistentCacheDir(opt.cacheIDNamespace+"/"+mount.CacheID, llb.CacheMountShared))
+			sharing := llb.CacheMountShared
+			if mount.CacheSharing == instructions.MountSharingPrivate {
+				sharing = llb.CacheMountPrivate
+			}
+			if mount.CacheSharing == instructions.MountSharingLocked {
+				sharing = llb.CacheMountLocked
+			}
+			mountOpts = append(mountOpts, llb.AsPersistentCacheDir(opt.cacheIDNamespace+"/"+mount.CacheID, sharing))
+		}
+		target := path.Join("/", mount.Target)
+		if target == "/" {
+			return nil, errors.Errorf("invalid mount target %q", mount.Target)
 		}
 		if src := path.Join("/", mount.Source); src != "/" {
 			mountOpts = append(mountOpts, llb.SourcePath(src))
 		}
-		out = append(out, llb.AddMount(path.Join("/", mount.Target), st, mountOpts...))
+		out = append(out, llb.AddMount(target, st, mountOpts...))
 
 		d.ctxPaths[path.Join("/", filepath.ToSlash(mount.Source))] = struct{}{}
 	}
-	return out
+	return out, nil
 }
diff --git a/frontend/dockerfile/instructions/commands_runmount.go b/frontend/dockerfile/instructions/commands_runmount.go
index 71030fa7..569c60bc 100644
--- a/frontend/dockerfile/instructions/commands_runmount.go
+++ b/frontend/dockerfile/instructions/commands_runmount.go
@@ -20,6 +20,16 @@ var allowedMountTypes = map[string]struct{}{
 	MountTypeTmpfs: {},
 }
 
+const MountSharingShared = "shared"
+const MountSharingPrivate = "private"
+const MountSharingLocked = "locked"
+
+var allowedSharingTypes = map[string]struct{}{
+	MountSharingShared:  {},
+	MountSharingPrivate: {},
+	MountSharingLocked:  {},
+}
+
 type mountsKeyT string
 
 var mountsKey = mountsKeyT("dockerfile/run/mounts")
@@ -76,12 +86,13 @@ type mountState struct {
 }
 
 type Mount struct {
-	Type     string
-	From     string
-	Source   string
-	Target   string
-	ReadOnly bool
-	CacheID  string
+	Type         string
+	From         string
+	Source       string
+	Target       string
+	ReadOnly     bool
+	CacheID      string
+	CacheSharing string
 }
 
 func parseMount(value string) (*Mount, error) {
@@ -120,7 +131,7 @@ func parseMount(value string) (*Mount, error) {
 		switch key {
 		case "type":
 			if !isValidMountType(strings.ToLower(value)) {
-				return nil, errors.Errorf("invalid mount type %q", value)
+				return nil, errors.Errorf("unsupported mount type %q", value)
 			}
 			m.Type = strings.ToLower(value)
 		case "from":
@@ -144,6 +155,11 @@ func parseMount(value string) (*Mount, error) {
 			roAuto = false
 		case "id":
 			m.CacheID = value
+		case "sharing":
+			if _, ok := allowedSharingTypes[strings.ToLower(value)]; !ok {
+				return nil, errors.Errorf("unsupported sharing value %q", value)
+			}
+			m.CacheSharing = strings.ToLower(value)
 		default:
 			return nil, errors.Errorf("unexpected key '%s' in '%s'", key, field)
 		}
@@ -157,5 +173,9 @@ func parseMount(value string) (*Mount, error) {
 		}
 	}
 
+	if m.CacheSharing != "" && m.Type != MountTypeCache {
+		return nil, errors.Errorf("invalid cache sharing set for %v mount", m.Type)
+	}
+
 	return m, nil
 }