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-rw-r--r--pkg/sentry/devices/memdev/BUILD5
-rw-r--r--pkg/sentry/devices/memdev/zero.go24
-rw-r--r--pkg/sentry/fsimpl/tmpfs/filesystem.go10
-rw-r--r--pkg/sentry/fsimpl/tmpfs/regular_file.go73
-rw-r--r--pkg/sentry/fsimpl/tmpfs/tmpfs.go31
-rw-r--r--pkg/sentry/mm/mm.go2
-rw-r--r--pkg/sentry/mm/mm_test.go3
-rw-r--r--pkg/sentry/mm/special_mappable.go9
-rw-r--r--pkg/sentry/mm/syscalls.go13
-rw-r--r--pkg/sentry/syscalls/linux/sys_mmap.go9
-rw-r--r--pkg/sentry/syscalls/linux/vfs2/mmap.go12
11 files changed, 129 insertions, 62 deletions
diff --git a/pkg/sentry/devices/memdev/BUILD b/pkg/sentry/devices/memdev/BUILD
index abe58f818..4c8604d58 100644
--- a/pkg/sentry/devices/memdev/BUILD
+++ b/pkg/sentry/devices/memdev/BUILD
@@ -18,9 +18,10 @@ go_library(
"//pkg/rand",
"//pkg/safemem",
"//pkg/sentry/fsimpl/devtmpfs",
+ "//pkg/sentry/fsimpl/tmpfs",
+ "//pkg/sentry/kernel",
+ "//pkg/sentry/kernel/auth",
"//pkg/sentry/memmap",
- "//pkg/sentry/mm",
- "//pkg/sentry/pgalloc",
"//pkg/sentry/vfs",
"//pkg/syserror",
"//pkg/usermem",
diff --git a/pkg/sentry/devices/memdev/zero.go b/pkg/sentry/devices/memdev/zero.go
index 2e631a252..60cfea888 100644
--- a/pkg/sentry/devices/memdev/zero.go
+++ b/pkg/sentry/devices/memdev/zero.go
@@ -16,9 +16,10 @@ package memdev
import (
"gvisor.dev/gvisor/pkg/context"
+ "gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
+ "gvisor.dev/gvisor/pkg/sentry/kernel"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/memmap"
- "gvisor.dev/gvisor/pkg/sentry/mm"
- "gvisor.dev/gvisor/pkg/sentry/pgalloc"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/usermem"
)
@@ -79,11 +80,22 @@ func (fd *zeroFD) Seek(ctx context.Context, offset int64, whence int32) (int64,
// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
func (fd *zeroFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
- m, err := mm.NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
+ if opts.Private || !opts.MaxPerms.Write {
+ // This mapping will never permit writing to the "underlying file" (in
+ // Linux terms, it isn't VM_SHARED), so implement it as an anonymous
+ // mapping, but back it with fd; this is what Linux does, and is
+ // actually application-visible because the resulting VMA will show up
+ // in /proc/[pid]/maps with fd.vfsfd.VirtualDentry()'s path rather than
+ // "/dev/zero (deleted)".
+ opts.Offset = 0
+ opts.MappingIdentity = &fd.vfsfd
+ opts.MappingIdentity.IncRef()
+ return nil
+ }
+ tmpfsFD, err := tmpfs.NewZeroFile(ctx, auth.CredentialsFromContext(ctx), kernel.KernelFromContext(ctx).ShmMount(), opts.Length)
if err != nil {
return err
}
- opts.MappingIdentity = m
- opts.Mappable = m
- return nil
+ defer tmpfsFD.DecRef(ctx)
+ return tmpfsFD.ConfigureMMap(ctx, opts)
}
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 99277093e..1362c1602 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -865,8 +865,16 @@ func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDe
}
if d.parent == nil {
if d.name != "" {
- // This must be an anonymous memfd file.
+ // This file must have been created by
+ // newUnlinkedRegularFileDescription(). In Linux,
+ // mm/shmem.c:__shmem_file_setup() =>
+ // fs/file_table.c:alloc_file_pseudo() sets the created
+ // dentry's dentry_operations to anon_ops, for which d_dname ==
+ // simple_dname. fs/d_path.c:simple_dname() defines the
+ // dentry's pathname to be its name, prefixed with "/" and
+ // suffixed with " (deleted)".
b.PrependComponent("/" + d.name)
+ b.AppendString(" (deleted)")
return vfs.PrependPathSyntheticError{}
}
return vfs.PrependPathAtNonMountRootError{}
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index 0710b65db..b8699d064 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -42,6 +42,10 @@ type regularFile struct {
// memFile is a platform.File used to allocate pages to this regularFile.
memFile *pgalloc.MemoryFile
+ // memoryUsageKind is the memory accounting category under which pages backing
+ // this regularFile's contents are accounted.
+ memoryUsageKind usage.MemoryKind
+
// mapsMu protects mappings.
mapsMu sync.Mutex `state:"nosave"`
@@ -86,14 +90,75 @@ type regularFile struct {
func (fs *filesystem) newRegularFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode) *inode {
file := &regularFile{
- memFile: fs.memFile,
- seals: linux.F_SEAL_SEAL,
+ memFile: fs.memFile,
+ memoryUsageKind: usage.Tmpfs,
+ seals: linux.F_SEAL_SEAL,
}
file.inode.init(file, fs, kuid, kgid, linux.S_IFREG|mode)
file.inode.nlink = 1 // from parent directory
return &file.inode
}
+// newUnlinkedRegularFileDescription creates a regular file on the tmpfs
+// filesystem represented by mount and returns an FD representing that file.
+// The new file is not reachable by path traversal from any other file.
+//
+// newUnlinkedRegularFileDescription is analogous to Linux's
+// mm/shmem.c:__shmem_file_setup().
+//
+// Preconditions: mount must be a tmpfs mount.
+func newUnlinkedRegularFileDescription(ctx context.Context, creds *auth.Credentials, mount *vfs.Mount, name string) (*regularFileFD, error) {
+ fs, ok := mount.Filesystem().Impl().(*filesystem)
+ if !ok {
+ panic("tmpfs.newUnlinkedRegularFileDescription() called with non-tmpfs mount")
+ }
+
+ inode := fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, 0777)
+ d := fs.newDentry(inode)
+ defer d.DecRef(ctx)
+ d.name = name
+
+ fd := &regularFileFD{}
+ fd.Init(&inode.locks)
+ flags := uint32(linux.O_RDWR)
+ if err := fd.vfsfd.Init(fd, flags, mount, &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
+ return nil, err
+ }
+ return fd, nil
+}
+
+// NewZeroFile creates a new regular file and file description as for
+// mmap(MAP_SHARED | MAP_ANONYMOUS). The file has the given size and is
+// initially (implicitly) filled with zeroes.
+//
+// Preconditions: mount must be a tmpfs mount.
+func NewZeroFile(ctx context.Context, creds *auth.Credentials, mount *vfs.Mount, size uint64) (*vfs.FileDescription, error) {
+ // Compare mm/shmem.c:shmem_zero_setup().
+ fd, err := newUnlinkedRegularFileDescription(ctx, creds, mount, "dev/zero")
+ if err != nil {
+ return nil, err
+ }
+ rf := fd.inode().impl.(*regularFile)
+ rf.memoryUsageKind = usage.Anonymous
+ rf.size = size
+ return &fd.vfsfd, err
+}
+
+// NewMemfd creates a new regular file and file description as for
+// memfd_create.
+//
+// Preconditions: mount must be a tmpfs mount.
+func NewMemfd(ctx context.Context, creds *auth.Credentials, mount *vfs.Mount, allowSeals bool, name string) (*vfs.FileDescription, error) {
+ fd, err := newUnlinkedRegularFileDescription(ctx, creds, mount, name)
+ if err != nil {
+ return nil, err
+ }
+ if allowSeals {
+ fd.inode().impl.(*regularFile).seals = 0
+ }
+ return &fd.vfsfd, nil
+}
+
// truncate grows or shrinks the file to the given size. It returns true if the
// file size was updated.
func (rf *regularFile) truncate(newSize uint64) (bool, error) {
@@ -226,7 +291,7 @@ func (rf *regularFile) Translate(ctx context.Context, required, optional memmap.
optional.End = pgend
}
- cerr := rf.data.Fill(ctx, required, optional, rf.memFile, usage.Tmpfs, func(_ context.Context, dsts safemem.BlockSeq, _ uint64) (uint64, error) {
+ cerr := rf.data.Fill(ctx, required, optional, rf.memFile, rf.memoryUsageKind, func(_ context.Context, dsts safemem.BlockSeq, _ uint64) (uint64, error) {
// Newly-allocated pages are zeroed, so we don't need to do anything.
return dsts.NumBytes(), nil
})
@@ -575,7 +640,7 @@ func (rw *regularFileReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64,
case gap.Ok():
// Allocate memory for the write.
gapMR := gap.Range().Intersect(pgMR)
- fr, err := rw.file.memFile.Allocate(gapMR.Length(), usage.Tmpfs)
+ fr, err := rw.file.memFile.Allocate(gapMR.Length(), rw.file.memoryUsageKind)
if err != nil {
retErr = err
goto exitLoop
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 4871e55d3..4658e1533 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -746,37 +746,6 @@ func (fd *fileDescription) RemoveXattr(ctx context.Context, name string) error {
return nil
}
-// NewMemfd creates a new tmpfs regular file and file description that can back
-// an anonymous fd created by memfd_create.
-func NewMemfd(ctx context.Context, creds *auth.Credentials, mount *vfs.Mount, allowSeals bool, name string) (*vfs.FileDescription, error) {
- fs, ok := mount.Filesystem().Impl().(*filesystem)
- if !ok {
- panic("NewMemfd() called with non-tmpfs mount")
- }
-
- // Per Linux, mm/shmem.c:__shmem_file_setup(), memfd inodes are set up with
- // S_IRWXUGO.
- inode := fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, 0777)
- rf := inode.impl.(*regularFile)
- if allowSeals {
- rf.seals = 0
- }
-
- d := fs.newDentry(inode)
- defer d.DecRef(ctx)
- d.name = name
-
- // Per Linux, mm/shmem.c:__shmem_file_setup(), memfd files are set up with
- // FMODE_READ | FMODE_WRITE.
- var fd regularFileFD
- fd.Init(&inode.locks)
- flags := uint32(linux.O_RDWR)
- if err := fd.vfsfd.Init(&fd, flags, mount, &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
- return nil, err
- }
- return &fd.vfsfd, nil
-}
-
// LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
func (fd *fileDescription) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, start, length uint64, whence int16, block fslock.Blocker) error {
return fd.Locks().LockPOSIX(ctx, &fd.vfsfd, uid, t, start, length, whence, block)
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index 3e85964e4..8c9f11cce 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -242,7 +242,7 @@ type MemoryManager struct {
// +stateify savable
type vma struct {
// mappable is the virtual memory object mapped by this vma. If mappable is
- // nil, the vma represents a private anonymous mapping.
+ // nil, the vma represents an anonymous mapping.
mappable memmap.Mappable
// off is the offset into mappable at which this vma begins. If mappable is
diff --git a/pkg/sentry/mm/mm_test.go b/pkg/sentry/mm/mm_test.go
index fdc308542..acac3d357 100644
--- a/pkg/sentry/mm/mm_test.go
+++ b/pkg/sentry/mm/mm_test.go
@@ -51,7 +51,8 @@ func TestUsageASUpdates(t *testing.T) {
defer mm.DecUsers(ctx)
addr, err := mm.MMap(ctx, memmap.MMapOpts{
- Length: 2 * usermem.PageSize,
+ Length: 2 * usermem.PageSize,
+ Private: true,
})
if err != nil {
t.Fatalf("MMap got err %v want nil", err)
diff --git a/pkg/sentry/mm/special_mappable.go b/pkg/sentry/mm/special_mappable.go
index f4c93baeb..2dbe5b751 100644
--- a/pkg/sentry/mm/special_mappable.go
+++ b/pkg/sentry/mm/special_mappable.go
@@ -136,9 +136,12 @@ func (m *SpecialMappable) Length() uint64 {
// NewSharedAnonMappable returns a SpecialMappable that implements the
// semantics of mmap(MAP_SHARED|MAP_ANONYMOUS) and mappings of /dev/zero.
//
-// TODO(jamieliu): The use of SpecialMappable is a lazy code reuse hack. Linux
-// uses an ephemeral file created by mm/shmem.c:shmem_zero_setup(); we should
-// do the same to get non-zero device and inode IDs.
+// TODO(gvisor.dev/issue/1624): Linux uses an ephemeral file created by
+// mm/shmem.c:shmem_zero_setup(), and VFS2 does something analogous. VFS1 uses
+// a SpecialMappable instead, incorrectly getting device and inode IDs of zero
+// and causing memory for shared anonymous mappings to be allocated up-front
+// instead of on first touch; this is to avoid exacerbating the fs.MountSource
+// leak (b/143656263). Delete this function along with VFS1.
func NewSharedAnonMappable(length uint64, mfp pgalloc.MemoryFileProvider) (*SpecialMappable, error) {
if length == 0 {
return nil, syserror.EINVAL
diff --git a/pkg/sentry/mm/syscalls.go b/pkg/sentry/mm/syscalls.go
index 4c9a575e7..a2555ba1a 100644
--- a/pkg/sentry/mm/syscalls.go
+++ b/pkg/sentry/mm/syscalls.go
@@ -24,7 +24,6 @@ import (
"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
"gvisor.dev/gvisor/pkg/sentry/limits"
"gvisor.dev/gvisor/pkg/sentry/memmap"
- "gvisor.dev/gvisor/pkg/sentry/pgalloc"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
@@ -93,18 +92,6 @@ func (mm *MemoryManager) MMap(ctx context.Context, opts memmap.MMapOpts) (userme
}
} else {
opts.Offset = 0
- if !opts.Private {
- if opts.MappingIdentity != nil {
- return 0, syserror.EINVAL
- }
- m, err := NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
- if err != nil {
- return 0, err
- }
- defer m.DecRef(ctx)
- opts.MappingIdentity = m
- opts.Mappable = m
- }
}
if opts.Addr.RoundDown() != opts.Addr {
diff --git a/pkg/sentry/syscalls/linux/sys_mmap.go b/pkg/sentry/syscalls/linux/sys_mmap.go
index 8ab062bca..cd8dfdfa4 100644
--- a/pkg/sentry/syscalls/linux/sys_mmap.go
+++ b/pkg/sentry/syscalls/linux/sys_mmap.go
@@ -100,6 +100,15 @@ func Mmap(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
if err := file.ConfigureMMap(t, &opts); err != nil {
return 0, nil, err
}
+ } else if shared {
+ // Back shared anonymous mappings with a special mappable.
+ opts.Offset = 0
+ m, err := mm.NewSharedAnonMappable(opts.Length, t.Kernel())
+ if err != nil {
+ return 0, nil, err
+ }
+ opts.MappingIdentity = m // transfers ownership of m to opts
+ opts.Mappable = m
}
rv, err := t.MemoryManager().MMap(t, opts)
diff --git a/pkg/sentry/syscalls/linux/vfs2/mmap.go b/pkg/sentry/syscalls/linux/vfs2/mmap.go
index dc05c2994..9d9dbf775 100644
--- a/pkg/sentry/syscalls/linux/vfs2/mmap.go
+++ b/pkg/sentry/syscalls/linux/vfs2/mmap.go
@@ -17,6 +17,7 @@ package vfs2
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
+ "gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/syserror"
@@ -85,6 +86,17 @@ func Mmap(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
if err := file.ConfigureMMap(t, &opts); err != nil {
return 0, nil, err
}
+ } else if shared {
+ // Back shared anonymous mappings with an anonymous tmpfs file.
+ opts.Offset = 0
+ file, err := tmpfs.NewZeroFile(t, t.Credentials(), t.Kernel().ShmMount(), opts.Length)
+ if err != nil {
+ return 0, nil, err
+ }
+ defer file.DecRef(t)
+ if err := file.ConfigureMMap(t, &opts); err != nil {
+ return 0, nil, err
+ }
}
rv, err := t.MemoryManager().MMap(t, opts)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-20 15:31:43 +0000