From 0e2f1b7abd219f39d67cc2cecd00c441a13eeb29 Mon Sep 17 00:00:00 2001 From: Adin Scannell Date: Mon, 27 Jan 2020 15:17:58 -0800 Subject: Update package locations. Because the abi will depend on the core types for marshalling (usermem, context, safemem, safecopy), these need to be flattened from the sentry directory. These packages contain no sentry-specific details. PiperOrigin-RevId: 291811289 --- pkg/sentry/vfs/vfs.go | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'pkg/sentry/vfs/vfs.go') diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index 1f6f56293..b2bf48853 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -31,8 +31,8 @@ import ( "fmt" "gvisor.dev/gvisor/pkg/abi/linux" + "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/fspath" - "gvisor.dev/gvisor/pkg/sentry/context" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" -- cgit v1.2.3 From 1119644080ae57c206b9b0d8d127cf48423af7f2 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Tue, 28 Jan 2020 12:06:58 -0800 Subject: Implement an anon_inode equivalent for VFS2. PiperOrigin-RevId: 291986033 --- pkg/sentry/vfs/BUILD | 3 +- pkg/sentry/vfs/anonfs.go | 259 ++++++++++++++++++++++ pkg/sentry/vfs/file_description_impl_util_test.go | 18 +- pkg/sentry/vfs/testutil.go | 173 --------------- pkg/sentry/vfs/vfs.go | 24 ++ 5 files changed, 289 insertions(+), 188 deletions(-) create mode 100644 pkg/sentry/vfs/anonfs.go delete mode 100644 pkg/sentry/vfs/testutil.go (limited to 'pkg/sentry/vfs/vfs.go') diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD index 6b1009328..33516e6f7 100644 --- a/pkg/sentry/vfs/BUILD +++ b/pkg/sentry/vfs/BUILD @@ -5,6 +5,7 @@ licenses(["notice"]) go_library( name = "vfs", srcs = [ + "anonfs.go", "context.go", "debug.go", "dentry.go", @@ -20,7 +21,6 @@ go_library( "pathname.go", "permissions.go", "resolving_path.go", - "testutil.go", "vfs.go", ], visibility = ["//pkg/sentry:internal"], @@ -50,7 +50,6 @@ go_test( "//pkg/abi/linux", "//pkg/context", "//pkg/sentry/contexttest", - "//pkg/sentry/kernel/auth", "//pkg/sync", "//pkg/syserror", "//pkg/usermem", diff --git a/pkg/sentry/vfs/anonfs.go b/pkg/sentry/vfs/anonfs.go new file mode 100644 index 000000000..2db25be49 --- /dev/null +++ b/pkg/sentry/vfs/anonfs.go @@ -0,0 +1,259 @@ +// Copyright 2020 The gVisor Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package vfs + +import ( + "fmt" + + "gvisor.dev/gvisor/pkg/abi/linux" + "gvisor.dev/gvisor/pkg/context" + "gvisor.dev/gvisor/pkg/fspath" + "gvisor.dev/gvisor/pkg/sentry/kernel/auth" + "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/usermem" +) + +// NewAnonVirtualDentry returns a VirtualDentry with the given synthetic name, +// consistent with Linux's fs/anon_inodes.c:anon_inode_getfile(). References +// are taken on the returned VirtualDentry. +func (vfs *VirtualFilesystem) NewAnonVirtualDentry(name string) VirtualDentry { + d := anonDentry{ + name: name, + } + d.vfsd.Init(&d) + vfs.anonMount.IncRef() + // anonDentry no-ops refcounting. + return VirtualDentry{ + mount: vfs.anonMount, + dentry: &d.vfsd, + } +} + +const anonfsBlockSize = usermem.PageSize // via fs/libfs.c:pseudo_fs_fill_super() + +// anonFilesystem is the implementation of FilesystemImpl that backs +// VirtualDentries returned by VirtualFilesystem.NewAnonVirtualDentry(). +// +// Since all Dentries in anonFilesystem are non-directories, all FilesystemImpl +// methods that would require an anonDentry to be a directory return ENOTDIR. +type anonFilesystem struct { + vfsfs Filesystem + + devMinor uint32 +} + +type anonDentry struct { + vfsd Dentry + + name string +} + +// Release implements FilesystemImpl.Release. +func (fs *anonFilesystem) Release() { +} + +// Sync implements FilesystemImpl.Sync. +func (fs *anonFilesystem) Sync(ctx context.Context) error { + return nil +} + +// GetDentryAt implements FilesystemImpl.GetDentryAt. +func (fs *anonFilesystem) GetDentryAt(ctx context.Context, rp *ResolvingPath, opts GetDentryOptions) (*Dentry, error) { + if !rp.Done() { + return nil, syserror.ENOTDIR + } + if opts.CheckSearchable { + return nil, syserror.ENOTDIR + } + // anonDentry no-ops refcounting. + return rp.Start(), nil +} + +// GetParentDentryAt implements FilesystemImpl.GetParentDentryAt. +func (fs *anonFilesystem) GetParentDentryAt(ctx context.Context, rp *ResolvingPath) (*Dentry, error) { + if !rp.Final() { + return nil, syserror.ENOTDIR + } + // anonDentry no-ops refcounting. + return rp.Start(), nil +} + +// LinkAt implements FilesystemImpl.LinkAt. +func (fs *anonFilesystem) LinkAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// MkdirAt implements FilesystemImpl.MkdirAt. +func (fs *anonFilesystem) MkdirAt(ctx context.Context, rp *ResolvingPath, opts MkdirOptions) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// MknodAt implements FilesystemImpl.MknodAt. +func (fs *anonFilesystem) MknodAt(ctx context.Context, rp *ResolvingPath, opts MknodOptions) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// OpenAt implements FilesystemImpl.OpenAt. +func (fs *anonFilesystem) OpenAt(ctx context.Context, rp *ResolvingPath, opts OpenOptions) (*FileDescription, error) { + if !rp.Done() { + return nil, syserror.ENOTDIR + } + return nil, syserror.ENODEV +} + +// ReadlinkAt implements FilesystemImpl.ReadlinkAt. +func (fs *anonFilesystem) ReadlinkAt(ctx context.Context, rp *ResolvingPath) (string, error) { + if !rp.Done() { + return "", syserror.ENOTDIR + } + return "", syserror.EINVAL +} + +// RenameAt implements FilesystemImpl.RenameAt. +func (fs *anonFilesystem) RenameAt(ctx context.Context, rp *ResolvingPath, oldParentVD VirtualDentry, oldName string, opts RenameOptions) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// RmdirAt implements FilesystemImpl.RmdirAt. +func (fs *anonFilesystem) RmdirAt(ctx context.Context, rp *ResolvingPath) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// SetStatAt implements FilesystemImpl.SetStatAt. +func (fs *anonFilesystem) SetStatAt(ctx context.Context, rp *ResolvingPath, opts SetStatOptions) error { + if !rp.Done() { + return syserror.ENOTDIR + } + // Linux actually permits anon_inode_inode's metadata to be set, which is + // visible to all users of anon_inode_inode. We just silently ignore + // metadata changes. + return nil +} + +// StatAt implements FilesystemImpl.StatAt. +func (fs *anonFilesystem) StatAt(ctx context.Context, rp *ResolvingPath, opts StatOptions) (linux.Statx, error) { + if !rp.Done() { + return linux.Statx{}, syserror.ENOTDIR + } + // See fs/anon_inodes.c:anon_inode_init() => fs/libfs.c:alloc_anon_inode(). + return linux.Statx{ + Mask: linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_SIZE | linux.STATX_BLOCKS, + Blksize: anonfsBlockSize, + Nlink: 1, + UID: uint32(auth.RootKUID), + GID: uint32(auth.RootKGID), + Mode: 0600, // no type is correct + Ino: 1, + Size: 0, + Blocks: 0, + DevMajor: 0, + DevMinor: fs.devMinor, + }, nil +} + +// StatFSAt implements FilesystemImpl.StatFSAt. +func (fs *anonFilesystem) StatFSAt(ctx context.Context, rp *ResolvingPath) (linux.Statfs, error) { + if !rp.Done() { + return linux.Statfs{}, syserror.ENOTDIR + } + return linux.Statfs{ + Type: linux.ANON_INODE_FS_MAGIC, + BlockSize: anonfsBlockSize, + }, nil +} + +// SymlinkAt implements FilesystemImpl.SymlinkAt. +func (fs *anonFilesystem) SymlinkAt(ctx context.Context, rp *ResolvingPath, target string) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// UnlinkAt implements FilesystemImpl.UnlinkAt. +func (fs *anonFilesystem) UnlinkAt(ctx context.Context, rp *ResolvingPath) error { + if !rp.Final() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// ListxattrAt implements FilesystemImpl.ListxattrAt. +func (fs *anonFilesystem) ListxattrAt(ctx context.Context, rp *ResolvingPath) ([]string, error) { + if !rp.Done() { + return nil, syserror.ENOTDIR + } + return nil, nil +} + +// GetxattrAt implements FilesystemImpl.GetxattrAt. +func (fs *anonFilesystem) GetxattrAt(ctx context.Context, rp *ResolvingPath, name string) (string, error) { + if !rp.Done() { + return "", syserror.ENOTDIR + } + return "", syserror.ENOTSUP +} + +// SetxattrAt implements FilesystemImpl.SetxattrAt. +func (fs *anonFilesystem) SetxattrAt(ctx context.Context, rp *ResolvingPath, opts SetxattrOptions) error { + if !rp.Done() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// RemovexattrAt implements FilesystemImpl.RemovexattrAt. +func (fs *anonFilesystem) RemovexattrAt(ctx context.Context, rp *ResolvingPath, name string) error { + if !rp.Done() { + return syserror.ENOTDIR + } + return syserror.EPERM +} + +// PrependPath implements FilesystemImpl.PrependPath. +func (fs *anonFilesystem) PrependPath(ctx context.Context, vfsroot, vd VirtualDentry, b *fspath.Builder) error { + b.PrependComponent(fmt.Sprintf("anon_inode:%s", vd.dentry.impl.(*anonDentry).name)) + return PrependPathSyntheticError{} +} + +// IncRef implements DentryImpl.IncRef. +func (d *anonDentry) IncRef() { + // no-op +} + +// TryIncRef implements DentryImpl.TryIncRef. +func (d *anonDentry) TryIncRef() bool { + return true +} + +// DecRef implements DentryImpl.DecRef. +func (d *anonDentry) DecRef() { + // no-op +} diff --git a/pkg/sentry/vfs/file_description_impl_util_test.go b/pkg/sentry/vfs/file_description_impl_util_test.go index 1720d325d..0f44e7c8c 100644 --- a/pkg/sentry/vfs/file_description_impl_util_test.go +++ b/pkg/sentry/vfs/file_description_impl_util_test.go @@ -24,7 +24,6 @@ import ( "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/sentry/contexttest" - "gvisor.dev/gvisor/pkg/sentry/kernel/auth" "gvisor.dev/gvisor/pkg/syserror" "gvisor.dev/gvisor/pkg/usermem" ) @@ -46,9 +45,11 @@ type genCountFD struct { count uint64 // accessed using atomic memory ops } -func newGenCountFD(mnt *Mount, vfsd *Dentry) *FileDescription { +func newGenCountFD(vfsObj *VirtualFilesystem) *FileDescription { + vd := vfsObj.NewAnonVirtualDentry("genCountFD") + defer vd.DecRef() var fd genCountFD - fd.vfsfd.Init(&fd, 0 /* statusFlags */, mnt, vfsd, &FileDescriptionOptions{}) + fd.vfsfd.Init(&fd, 0 /* statusFlags */, vd.Mount(), vd.Dentry(), &FileDescriptionOptions{}) fd.DynamicBytesFileDescriptionImpl.SetDataSource(&fd) return &fd.vfsfd } @@ -86,18 +87,9 @@ func (fd *genCountFD) Generate(ctx context.Context, buf *bytes.Buffer) error { func TestGenCountFD(t *testing.T) { ctx := contexttest.Context(t) - creds := auth.CredentialsFromContext(ctx) vfsObj := New() // vfs.New() - vfsObj.MustRegisterFilesystemType("testfs", FDTestFilesystemType{}, &RegisterFilesystemTypeOptions{}) - mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "testfs", &GetFilesystemOptions{}) - if err != nil { - t.Fatalf("failed to create testfs root mount: %v", err) - } - vd := mntns.Root() - defer vd.DecRef() - - fd := newGenCountFD(vd.Mount(), vd.Dentry()) + fd := newGenCountFD(vfsObj) defer fd.DecRef() // The first read causes Generate to be called to fill the FD's buffer. diff --git a/pkg/sentry/vfs/testutil.go b/pkg/sentry/vfs/testutil.go deleted file mode 100644 index 392c7611e..000000000 --- a/pkg/sentry/vfs/testutil.go +++ /dev/null @@ -1,173 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package vfs - -import ( - "fmt" - - "gvisor.dev/gvisor/pkg/abi/linux" - "gvisor.dev/gvisor/pkg/context" - "gvisor.dev/gvisor/pkg/fspath" - "gvisor.dev/gvisor/pkg/sentry/kernel/auth" - "gvisor.dev/gvisor/pkg/syserror" -) - -// FDTestFilesystemType is a test-only FilesystemType that produces Filesystems -// for which all FilesystemImpl methods taking a path return EPERM. It is used -// to produce Mounts and Dentries for testing of FileDescriptionImpls that do -// not depend on their originating Filesystem. -type FDTestFilesystemType struct{} - -// FDTestFilesystem is a test-only FilesystemImpl produced by -// FDTestFilesystemType. -type FDTestFilesystem struct { - vfsfs Filesystem -} - -// GetFilesystem implements FilesystemType.GetFilesystem. -func (fstype FDTestFilesystemType) GetFilesystem(ctx context.Context, vfsObj *VirtualFilesystem, creds *auth.Credentials, source string, opts GetFilesystemOptions) (*Filesystem, *Dentry, error) { - var fs FDTestFilesystem - fs.vfsfs.Init(vfsObj, &fs) - return &fs.vfsfs, fs.NewDentry(), nil -} - -// Release implements FilesystemImpl.Release. -func (fs *FDTestFilesystem) Release() { -} - -// Sync implements FilesystemImpl.Sync. -func (fs *FDTestFilesystem) Sync(ctx context.Context) error { - return nil -} - -// GetDentryAt implements FilesystemImpl.GetDentryAt. -func (fs *FDTestFilesystem) GetDentryAt(ctx context.Context, rp *ResolvingPath, opts GetDentryOptions) (*Dentry, error) { - return nil, syserror.EPERM -} - -// GetParentDentryAt implements FilesystemImpl.GetParentDentryAt. -func (fs *FDTestFilesystem) GetParentDentryAt(ctx context.Context, rp *ResolvingPath) (*Dentry, error) { - return nil, syserror.EPERM -} - -// LinkAt implements FilesystemImpl.LinkAt. -func (fs *FDTestFilesystem) LinkAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry) error { - return syserror.EPERM -} - -// MkdirAt implements FilesystemImpl.MkdirAt. -func (fs *FDTestFilesystem) MkdirAt(ctx context.Context, rp *ResolvingPath, opts MkdirOptions) error { - return syserror.EPERM -} - -// MknodAt implements FilesystemImpl.MknodAt. -func (fs *FDTestFilesystem) MknodAt(ctx context.Context, rp *ResolvingPath, opts MknodOptions) error { - return syserror.EPERM -} - -// OpenAt implements FilesystemImpl.OpenAt. -func (fs *FDTestFilesystem) OpenAt(ctx context.Context, rp *ResolvingPath, opts OpenOptions) (*FileDescription, error) { - return nil, syserror.EPERM -} - -// ReadlinkAt implements FilesystemImpl.ReadlinkAt. -func (fs *FDTestFilesystem) ReadlinkAt(ctx context.Context, rp *ResolvingPath) (string, error) { - return "", syserror.EPERM -} - -// RenameAt implements FilesystemImpl.RenameAt. -func (fs *FDTestFilesystem) RenameAt(ctx context.Context, rp *ResolvingPath, oldParentVD VirtualDentry, oldName string, opts RenameOptions) error { - return syserror.EPERM -} - -// RmdirAt implements FilesystemImpl.RmdirAt. -func (fs *FDTestFilesystem) RmdirAt(ctx context.Context, rp *ResolvingPath) error { - return syserror.EPERM -} - -// SetStatAt implements FilesystemImpl.SetStatAt. -func (fs *FDTestFilesystem) SetStatAt(ctx context.Context, rp *ResolvingPath, opts SetStatOptions) error { - return syserror.EPERM -} - -// StatAt implements FilesystemImpl.StatAt. -func (fs *FDTestFilesystem) StatAt(ctx context.Context, rp *ResolvingPath, opts StatOptions) (linux.Statx, error) { - return linux.Statx{}, syserror.EPERM -} - -// StatFSAt implements FilesystemImpl.StatFSAt. -func (fs *FDTestFilesystem) StatFSAt(ctx context.Context, rp *ResolvingPath) (linux.Statfs, error) { - return linux.Statfs{}, syserror.EPERM -} - -// SymlinkAt implements FilesystemImpl.SymlinkAt. -func (fs *FDTestFilesystem) SymlinkAt(ctx context.Context, rp *ResolvingPath, target string) error { - return syserror.EPERM -} - -// UnlinkAt implements FilesystemImpl.UnlinkAt. -func (fs *FDTestFilesystem) UnlinkAt(ctx context.Context, rp *ResolvingPath) error { - return syserror.EPERM -} - -// ListxattrAt implements FilesystemImpl.ListxattrAt. -func (fs *FDTestFilesystem) ListxattrAt(ctx context.Context, rp *ResolvingPath) ([]string, error) { - return nil, syserror.EPERM -} - -// GetxattrAt implements FilesystemImpl.GetxattrAt. -func (fs *FDTestFilesystem) GetxattrAt(ctx context.Context, rp *ResolvingPath, name string) (string, error) { - return "", syserror.EPERM -} - -// SetxattrAt implements FilesystemImpl.SetxattrAt. -func (fs *FDTestFilesystem) SetxattrAt(ctx context.Context, rp *ResolvingPath, opts SetxattrOptions) error { - return syserror.EPERM -} - -// RemovexattrAt implements FilesystemImpl.RemovexattrAt. -func (fs *FDTestFilesystem) RemovexattrAt(ctx context.Context, rp *ResolvingPath, name string) error { - return syserror.EPERM -} - -// PrependPath implements FilesystemImpl.PrependPath. -func (fs *FDTestFilesystem) PrependPath(ctx context.Context, vfsroot, vd VirtualDentry, b *fspath.Builder) error { - b.PrependComponent(fmt.Sprintf("vfs.fdTestDentry:%p", vd.dentry.impl.(*fdTestDentry))) - return PrependPathSyntheticError{} -} - -type fdTestDentry struct { - vfsd Dentry -} - -// NewDentry returns a new Dentry. -func (fs *FDTestFilesystem) NewDentry() *Dentry { - var d fdTestDentry - d.vfsd.Init(&d) - return &d.vfsd -} - -// IncRef implements DentryImpl.IncRef. -func (d *fdTestDentry) IncRef() { -} - -// TryIncRef implements DentryImpl.TryIncRef. -func (d *fdTestDentry) TryIncRef() bool { - return true -} - -// DecRef implements DentryImpl.DecRef. -func (d *fdTestDentry) DecRef() { -} diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index b2bf48853..d730530b9 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -75,6 +75,14 @@ type VirtualFilesystem struct { // mountpoints is analogous to Linux's mountpoint_hashtable. mountpoints map[*Dentry]map[*Mount]struct{} + // anonMount is a Mount, not included in mounts or mountpoints, + // representing an anonFilesystem. anonMount is used to back + // VirtualDentries returned by VirtualFilesystem.NewAnonVirtualDentry(). + // anonMount is immutable. + // + // anonMount is analogous to Linux's anon_inode_mnt. + anonMount *Mount + // devices contains all registered Devices. devices is protected by // devicesMu. devicesMu sync.RWMutex @@ -110,6 +118,22 @@ func New() *VirtualFilesystem { filesystems: make(map[*Filesystem]struct{}), } vfs.mounts.Init() + + // Construct vfs.anonMount. + anonfsDevMinor, err := vfs.GetAnonBlockDevMinor() + if err != nil { + panic(fmt.Sprintf("VirtualFilesystem.GetAnonBlockDevMinor() failed during VirtualFilesystem construction: %v", err)) + } + anonfs := anonFilesystem{ + devMinor: anonfsDevMinor, + } + anonfs.vfsfs.Init(vfs, &anonfs) + vfs.anonMount = &Mount{ + vfs: vfs, + fs: &anonfs.vfsfs, + refs: 1, + } + return vfs } -- cgit v1.2.3 From 34fbd8446c386fb0136dad31ab6b173f17049a58 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Tue, 28 Jan 2020 13:10:41 -0800 Subject: Add VFS2 support for epoll. PiperOrigin-RevId: 291997879 --- pkg/abi/linux/epoll.go | 10 +- pkg/sentry/vfs/BUILD | 15 ++ pkg/sentry/vfs/epoll.go | 377 +++++++++++++++++++++++++++++++++++++ pkg/sentry/vfs/file_description.go | 38 ++++ pkg/sentry/vfs/vfs.go | 16 +- 5 files changed, 448 insertions(+), 8 deletions(-) create mode 100644 pkg/sentry/vfs/epoll.go (limited to 'pkg/sentry/vfs/vfs.go') diff --git a/pkg/abi/linux/epoll.go b/pkg/abi/linux/epoll.go index 72083b604..0e881aa3c 100644 --- a/pkg/abi/linux/epoll.go +++ b/pkg/abi/linux/epoll.go @@ -38,8 +38,14 @@ const ( // Per-file descriptor flags. const ( - EPOLLET = 0x80000000 - EPOLLONESHOT = 0x40000000 + EPOLLEXCLUSIVE = 1 << 28 + EPOLLWAKEUP = 1 << 29 + EPOLLONESHOT = 1 << 30 + EPOLLET = 1 << 31 + + // EP_PRIVATE_BITS is fs/eventpoll.c:EP_PRIVATE_BITS, the set of all bits + // in an epoll event mask that correspond to flags rather than I/O events. + EP_PRIVATE_BITS = EPOLLEXCLUSIVE | EPOLLWAKEUP | EPOLLONESHOT | EPOLLET ) // Operation flags. diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD index 33516e6f7..ced9d07b1 100644 --- a/pkg/sentry/vfs/BUILD +++ b/pkg/sentry/vfs/BUILD @@ -1,7 +1,20 @@ load("//tools:defs.bzl", "go_library", "go_test") +load("//tools/go_generics:defs.bzl", "go_template_instance") licenses(["notice"]) +go_template_instance( + name = "epoll_interest_list", + out = "epoll_interest_list.go", + package = "vfs", + prefix = "epollInterest", + template = "//pkg/ilist:generic_list", + types = { + "Element": "*epollInterest", + "Linker": "*epollInterest", + }, +) + go_library( name = "vfs", srcs = [ @@ -10,6 +23,8 @@ go_library( "debug.go", "dentry.go", "device.go", + "epoll.go", + "epoll_interest_list.go", "file_description.go", "file_description_impl_util.go", "filesystem.go", diff --git a/pkg/sentry/vfs/epoll.go b/pkg/sentry/vfs/epoll.go new file mode 100644 index 000000000..7c83f9a5a --- /dev/null +++ b/pkg/sentry/vfs/epoll.go @@ -0,0 +1,377 @@ +// Copyright 2020 The gVisor Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package vfs + +import ( + "gvisor.dev/gvisor/pkg/abi/linux" + "gvisor.dev/gvisor/pkg/context" + "gvisor.dev/gvisor/pkg/sync" + "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/waiter" +) + +// epollCycleMu serializes attempts to register EpollInstances with other +// EpollInstances in order to check for cycles. +var epollCycleMu sync.Mutex + +// EpollInstance represents an epoll instance, as described by epoll(7). +type EpollInstance struct { + vfsfd FileDescription + FileDescriptionDefaultImpl + DentryMetadataFileDescriptionImpl + + // q holds waiters on this EpollInstance. + q waiter.Queue + + // interest is the set of file descriptors that are registered with the + // EpollInstance for monitoring. interest is protected by interestMu. + interestMu sync.Mutex + interest map[epollInterestKey]*epollInterest + + // mu protects fields in registered epollInterests. + mu sync.Mutex + + // ready is the set of file descriptors that may be "ready" for I/O. Note + // that this must be an ordered list, not a map: "If more than maxevents + // file descriptors are ready when epoll_wait() is called, then successive + // epoll_wait() calls will round robin through the set of ready file + // descriptors. This behavior helps avoid starvation scenarios, where a + // process fails to notice that additional file descriptors are ready + // because it focuses on a set of file descriptors that are already known + // to be ready." - epoll_wait(2) + ready epollInterestList +} + +type epollInterestKey struct { + // file is the registered FileDescription. No reference is held on file; + // instead, when the last reference is dropped, FileDescription.DecRef() + // removes the FileDescription from all EpollInstances. file is immutable. + file *FileDescription + + // num is the file descriptor number with which this entry was registered. + // num is immutable. + num int32 +} + +// epollInterest represents an EpollInstance's interest in a file descriptor. +type epollInterest struct { + // epoll is the owning EpollInstance. epoll is immutable. + epoll *EpollInstance + + // key is the file to which this epollInterest applies. key is immutable. + key epollInterestKey + + // waiter is registered with key.file. entry is protected by epoll.mu. + waiter waiter.Entry + + // mask is the event mask associated with this registration, including + // flags EPOLLET and EPOLLONESHOT. mask is protected by epoll.mu. + mask uint32 + + // ready is true if epollInterestEntry is linked into epoll.ready. ready + // and epollInterestEntry are protected by epoll.mu. + ready bool + epollInterestEntry + + // userData is the epoll_data_t associated with this epollInterest. + // userData is protected by epoll.mu. + userData [2]int32 +} + +// NewEpollInstanceFD returns a FileDescription representing a new epoll +// instance. A reference is taken on the returned FileDescription. +func (vfs *VirtualFilesystem) NewEpollInstanceFD() (*FileDescription, error) { + vd := vfs.NewAnonVirtualDentry("[eventpoll]") + defer vd.DecRef() + ep := &EpollInstance{ + interest: make(map[epollInterestKey]*epollInterest), + } + if err := ep.vfsfd.Init(ep, linux.O_RDWR, vd.Mount(), vd.Dentry(), &FileDescriptionOptions{ + UseDentryMetadata: true, + }); err != nil { + return nil, err + } + return &ep.vfsfd, nil +} + +// Release implements FileDescriptionImpl.Release. +func (ep *EpollInstance) Release() { + // Unregister all polled fds. + ep.interestMu.Lock() + defer ep.interestMu.Unlock() + for key, epi := range ep.interest { + file := key.file + file.epollMu.Lock() + delete(file.epolls, epi) + file.epollMu.Unlock() + file.EventUnregister(&epi.waiter) + } + ep.interest = nil +} + +// Readiness implements waiter.Waitable.Readiness. +func (ep *EpollInstance) Readiness(mask waiter.EventMask) waiter.EventMask { + if mask&waiter.EventIn == 0 { + return 0 + } + ep.mu.Lock() + for epi := ep.ready.Front(); epi != nil; epi = epi.Next() { + wmask := waiter.EventMaskFromLinux(epi.mask) + if epi.key.file.Readiness(wmask)&wmask != 0 { + ep.mu.Unlock() + return waiter.EventIn + } + } + ep.mu.Unlock() + return 0 +} + +// EventRegister implements waiter.Waitable.EventRegister. +func (ep *EpollInstance) EventRegister(e *waiter.Entry, mask waiter.EventMask) { + ep.q.EventRegister(e, mask) +} + +// EventUnregister implements waiter.Waitable.EventUnregister. +func (ep *EpollInstance) EventUnregister(e *waiter.Entry) { + ep.q.EventUnregister(e) +} + +// Seek implements FileDescriptionImpl.Seek. +func (ep *EpollInstance) Seek(ctx context.Context, offset int64, whence int32) (int64, error) { + // Linux: fs/eventpoll.c:eventpoll_fops.llseek == noop_llseek + return 0, nil +} + +// AddInterest implements the semantics of EPOLL_CTL_ADD. +// +// Preconditions: A reference must be held on file. +func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, mask uint32, userData [2]int32) error { + // Check for cyclic polling if necessary. + subep, _ := file.impl.(*EpollInstance) + if subep != nil { + epollCycleMu.Lock() + // epollCycleMu must be locked for the rest of AddInterest to ensure + // that cyclic polling is not introduced after the check. + defer epollCycleMu.Unlock() + if subep.mightPoll(ep) { + return syserror.ELOOP + } + } + + ep.interestMu.Lock() + defer ep.interestMu.Unlock() + + // Fail if the key is already registered. + key := epollInterestKey{ + file: file, + num: num, + } + if _, ok := ep.interest[key]; ok { + return syserror.EEXIST + } + + // Register interest in file. + mask |= linux.EPOLLERR | linux.EPOLLRDHUP + epi := &epollInterest{ + epoll: ep, + key: key, + mask: mask, + userData: userData, + } + ep.interest[key] = epi + wmask := waiter.EventMaskFromLinux(mask) + file.EventRegister(&epi.waiter, wmask) + + // Check if the file is already ready. + if file.Readiness(wmask)&wmask != 0 { + epi.Callback(nil) + } + + // Add epi to file.epolls so that it is removed when the last + // FileDescription reference is dropped. + file.epollMu.Lock() + file.epolls[epi] = struct{}{} + file.epollMu.Unlock() + + return nil +} + +func (ep *EpollInstance) mightPoll(ep2 *EpollInstance) bool { + return ep.mightPollRecursive(ep2, 4) // Linux: fs/eventpoll.c:EP_MAX_NESTS +} + +func (ep *EpollInstance) mightPollRecursive(ep2 *EpollInstance, remainingRecursion int) bool { + ep.interestMu.Lock() + defer ep.interestMu.Unlock() + for key := range ep.interest { + nextep, ok := key.file.impl.(*EpollInstance) + if !ok { + continue + } + if nextep == ep2 { + return true + } + if remainingRecursion == 0 { + return true + } + if nextep.mightPollRecursive(ep2, remainingRecursion-1) { + return true + } + } + return false +} + +// ModifyInterest implements the semantics of EPOLL_CTL_MOD. +// +// Preconditions: A reference must be held on file. +func (ep *EpollInstance) ModifyInterest(file *FileDescription, num int32, mask uint32, userData [2]int32) error { + ep.interestMu.Lock() + defer ep.interestMu.Unlock() + + // Fail if the key is not already registered. + epi, ok := ep.interest[epollInterestKey{ + file: file, + num: num, + }] + if !ok { + return syserror.ENOENT + } + + // Update epi for the next call to ep.ReadEvents(). + ep.mu.Lock() + epi.mask = mask + epi.userData = userData + ep.mu.Unlock() + + // Re-register with the new mask. + mask |= linux.EPOLLERR | linux.EPOLLRDHUP + file.EventUnregister(&epi.waiter) + wmask := waiter.EventMaskFromLinux(mask) + file.EventRegister(&epi.waiter, wmask) + + // Check if the file is already ready with the new mask. + if file.Readiness(wmask)&wmask != 0 { + epi.Callback(nil) + } + + return nil +} + +// DeleteInterest implements the semantics of EPOLL_CTL_DEL. +// +// Preconditions: A reference must be held on file. +func (ep *EpollInstance) DeleteInterest(file *FileDescription, num int32) error { + ep.interestMu.Lock() + defer ep.interestMu.Unlock() + + // Fail if the key is not already registered. + epi, ok := ep.interest[epollInterestKey{ + file: file, + num: num, + }] + if !ok { + return syserror.ENOENT + } + + // Unregister from the file so that epi will no longer be readied. + file.EventUnregister(&epi.waiter) + + // Forget about epi. + ep.removeLocked(epi) + + file.epollMu.Lock() + delete(file.epolls, epi) + file.epollMu.Unlock() + + return nil +} + +// Callback implements waiter.EntryCallback.Callback. +func (epi *epollInterest) Callback(*waiter.Entry) { + newReady := false + epi.epoll.mu.Lock() + if !epi.ready { + newReady = true + epi.ready = true + epi.epoll.ready.PushBack(epi) + } + epi.epoll.mu.Unlock() + if newReady { + epi.epoll.q.Notify(waiter.EventIn) + } +} + +// Preconditions: ep.interestMu must be locked. +func (ep *EpollInstance) removeLocked(epi *epollInterest) { + delete(ep.interest, epi.key) + ep.mu.Lock() + if epi.ready { + epi.ready = false + ep.ready.Remove(epi) + } + ep.mu.Unlock() +} + +// ReadEvents reads up to len(events) ready events into events and returns the +// number of events read. +// +// Preconditions: len(events) != 0. +func (ep *EpollInstance) ReadEvents(events []linux.EpollEvent) int { + i := 0 + // Hot path: avoid defer. + ep.mu.Lock() + var next *epollInterest + var requeue epollInterestList + for epi := ep.ready.Front(); epi != nil; epi = next { + next = epi.Next() + // Regardless of what else happens, epi is initially removed from the + // ready list. + ep.ready.Remove(epi) + wmask := waiter.EventMaskFromLinux(epi.mask) + ievents := epi.key.file.Readiness(wmask) & wmask + if ievents == 0 { + // Leave epi off the ready list. + epi.ready = false + continue + } + // Determine what we should do with epi. + switch { + case epi.mask&linux.EPOLLONESHOT != 0: + // Clear all events from the mask; they must be re-added by + // EPOLL_CTL_MOD. + epi.mask &= linux.EP_PRIVATE_BITS + fallthrough + case epi.mask&linux.EPOLLET != 0: + // Leave epi off the ready list. + epi.ready = false + default: + // Queue epi to be moved to the end of the ready list. + requeue.PushBack(epi) + } + // Report ievents. + events[i] = linux.EpollEvent{ + Events: ievents.ToLinux(), + Fd: epi.userData[0], + Data: epi.userData[1], + } + i++ + if i == len(events) { + break + } + } + ep.ready.PushBackList(&requeue) + ep.mu.Unlock() + return i +} diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go index 225024463..badacb55e 100644 --- a/pkg/sentry/vfs/file_description.go +++ b/pkg/sentry/vfs/file_description.go @@ -22,6 +22,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/arch" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" "gvisor.dev/gvisor/pkg/sentry/memmap" + "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" "gvisor.dev/gvisor/pkg/usermem" "gvisor.dev/gvisor/pkg/waiter" @@ -45,6 +46,11 @@ type FileDescription struct { // memory operations. statusFlags uint32 + // epolls is the set of epollInterests registered for this FileDescription. + // epolls is protected by epollMu. + epollMu sync.Mutex + epolls map[*epollInterest]struct{} + // vd is the filesystem location at which this FileDescription was opened. // A reference is held on vd. vd is immutable. vd VirtualDentry @@ -141,6 +147,23 @@ func (fd *FileDescription) TryIncRef() bool { // DecRef decrements fd's reference count. func (fd *FileDescription) DecRef() { if refs := atomic.AddInt64(&fd.refs, -1); refs == 0 { + // Unregister fd from all epoll instances. + fd.epollMu.Lock() + epolls := fd.epolls + fd.epolls = nil + fd.epollMu.Unlock() + for epi := range epolls { + ep := epi.epoll + ep.interestMu.Lock() + // Check that epi has not been concurrently unregistered by + // EpollInstance.DeleteInterest() or EpollInstance.Release(). + if _, ok := ep.interest[epi.key]; ok { + fd.EventUnregister(&epi.waiter) + ep.removeLocked(epi) + } + ep.interestMu.Unlock() + } + // Release implementation resources. fd.impl.Release() if fd.writable { fd.vd.mount.EndWrite() @@ -453,6 +476,21 @@ func (fd *FileDescription) StatFS(ctx context.Context) (linux.Statfs, error) { return fd.impl.StatFS(ctx) } +// Readiness returns fd's I/O readiness. +func (fd *FileDescription) Readiness(mask waiter.EventMask) waiter.EventMask { + return fd.impl.Readiness(mask) +} + +// EventRegister registers e for I/O readiness events in mask. +func (fd *FileDescription) EventRegister(e *waiter.Entry, mask waiter.EventMask) { + fd.impl.EventRegister(e, mask) +} + +// EventUnregister unregisters e for I/O readiness events. +func (fd *FileDescription) EventUnregister(e *waiter.Entry) { + fd.impl.EventUnregister(e) +} + // PRead reads from the file represented by fd into dst, starting at the given // offset, and returns the number of bytes read. PRead is permitted to return // partial reads with a nil error. diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index d730530b9..908c69f91 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -16,15 +16,19 @@ // // Lock order: // -// FilesystemImpl/FileDescriptionImpl locks -// VirtualFilesystem.mountMu -// Dentry.mu -// Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry -// VirtualFilesystem.filesystemsMu +// EpollInstance.interestMu +// FileDescription.epollMu +// FilesystemImpl/FileDescriptionImpl locks +// VirtualFilesystem.mountMu +// Dentry.mu +// Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry +// VirtualFilesystem.filesystemsMu +// EpollInstance.mu // VirtualFilesystem.fsTypesMu // // Locking Dentry.mu in multiple Dentries requires holding -// VirtualFilesystem.mountMu. +// VirtualFilesystem.mountMu. Locking EpollInstance.interestMu in multiple +// EpollInstances requires holding epollCycleMu. package vfs import ( -- cgit v1.2.3