From d3b19e94842e8b3a2b387f3e306b1d7a3e06dd6f Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@google.com>
Date: Thu, 24 Aug 2023 22:55:55 -0700
Subject: [PATCH] proc: add /proc/{bus,fs,irq,sysrq-trigger}

Docker fails starting a container without these paths. All of them are
enumerated in readonlyPaths of a container spec.

PiperOrigin-RevId: 559984658
---
 pkg/sentry/fsimpl/proc/filesystem.go | 9 +++++++++
 pkg/sentry/fsimpl/proc/tasks.go      | 4 ++++
 pkg/sentry/fsimpl/proc/tasks_test.go | 4 ++++
 3 files changed, 17 insertions(+)

diff --git a/pkg/sentry/fsimpl/proc/filesystem.go b/pkg/sentry/fsimpl/proc/filesystem.go
index f2697c12d..5c282b795 100644
--- a/pkg/sentry/fsimpl/proc/filesystem.go
+++ b/pkg/sentry/fsimpl/proc/filesystem.go
@@ -54,6 +54,15 @@ type filesystem struct {
 	devMinor uint32
 }
 
+func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linux.Statfs, error) {
+	d, err := fs.GetDentryAt(ctx, rp, vfs.GetDentryOptions{})
+	if err != nil {
+		return linux.Statfs{}, err
+	}
+	d.DecRef(ctx)
+	return vfs.GenericStatFS(linux.PROC_SUPER_MAGIC), nil
+}
+
 // GetFilesystem implements vfs.FilesystemType.GetFilesystem.
 func (ft FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
 	k := kernel.KernelFromContext(ctx)
diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go
index b9c743b5c..b3239f8bd 100644
--- a/pkg/sentry/fsimpl/proc/tasks.go
+++ b/pkg/sentry/fsimpl/proc/tasks.go
@@ -72,11 +72,15 @@ func (fs *filesystem) newTasksInode(ctx context.Context, k *kernel.Kernel, pidns
 		"filesystems":    fs.newInode(ctx, root, 0444, &filesystemsData{}),
 		"loadavg":        fs.newInode(ctx, root, 0444, &loadavgData{}),
 		"sys":            fs.newSysDir(ctx, root, k),
+		"bus":            fs.newStaticDir(ctx, root, map[string]kernfs.Inode{}),
+		"fs":             fs.newStaticDir(ctx, root, map[string]kernfs.Inode{}),
+		"irq":            fs.newStaticDir(ctx, root, map[string]kernfs.Inode{}),
 		"meminfo":        fs.newInode(ctx, root, 0444, &meminfoData{}),
 		"mounts":         kernfs.NewStaticSymlink(ctx, root, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), "self/mounts"),
 		"net":            kernfs.NewStaticSymlink(ctx, root, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), "self/net"),
 		"sentry-meminfo": fs.newInode(ctx, root, 0444, &sentryMeminfoData{}),
 		"stat":           fs.newInode(ctx, root, 0444, &statData{}),
+		"sysrq-trigger":  fs.newInode(ctx, root, 0200, newStaticFile("")),
 		"uptime":         fs.newInode(ctx, root, 0444, &uptimeData{}),
 		"version":        fs.newInode(ctx, root, 0444, &versionData{}),
 	}
diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go
index 4b671a9a9..68c5d468d 100644
--- a/pkg/sentry/fsimpl/proc/tasks_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_test.go
@@ -47,9 +47,12 @@ var (
 
 var (
 	tasksStaticFiles = map[string]testutil.DirentType{
+		"bus":            linux.DT_DIR,
 		"cmdline":        linux.DT_REG,
 		"cpuinfo":        linux.DT_REG,
 		"filesystems":    linux.DT_REG,
+		"fs":             linux.DT_DIR,
+		"irq":            linux.DT_DIR,
 		"loadavg":        linux.DT_REG,
 		"meminfo":        linux.DT_REG,
 		"mounts":         linux.DT_LNK,
@@ -58,6 +61,7 @@ var (
 		"sentry-meminfo": linux.DT_REG,
 		"stat":           linux.DT_REG,
 		"sys":            linux.DT_DIR,
+		"sysrq-trigger":  linux.DT_REG,
 		"thread-self":    linux.DT_LNK,
 		"uptime":         linux.DT_REG,
 		"version":        linux.DT_REG,