diff options
Diffstat (limited to 'pkg/sentry')
-rw-r--r-- | pkg/sentry/fs/attr.go | 14 | ||||
-rw-r--r-- | pkg/sentry/fs/dev/dev.go | 8 | ||||
-rw-r--r-- | pkg/sentry/fs/fsutil/host_mappable.go | 21 | ||||
-rw-r--r-- | pkg/sentry/fs/fsutil/inode_cached.go | 27 | ||||
-rw-r--r-- | pkg/sentry/fs/gofer/file.go | 16 | ||||
-rw-r--r-- | pkg/sentry/fs/gofer/inode.go | 18 | ||||
-rw-r--r-- | pkg/sentry/fs/gofer/path.go | 20 | ||||
-rw-r--r-- | pkg/sentry/fs/tmpfs/fs.go | 2 | ||||
-rw-r--r-- | pkg/sentry/fs/tmpfs/inode_file.go | 15 | ||||
-rw-r--r-- | pkg/sentry/fs/tmpfs/tmpfs.go | 31 | ||||
-rw-r--r-- | pkg/sentry/fs/user/user_test.go | 5 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/overlay/regular_file.go | 13 | ||||
-rw-r--r-- | pkg/sentry/syscalls/linux/sys_file.go | 22 |
13 files changed, 182 insertions, 30 deletions
diff --git a/pkg/sentry/fs/attr.go b/pkg/sentry/fs/attr.go index b90f7c1be..4c99944e7 100644 --- a/pkg/sentry/fs/attr.go +++ b/pkg/sentry/fs/attr.go @@ -478,6 +478,20 @@ func (f FilePermissions) AnyRead() bool { return f.User.Read || f.Group.Read || f.Other.Read } +// HasSetUIDOrGID returns true if either the setuid or setgid bit is set. +func (f FilePermissions) HasSetUIDOrGID() bool { + return f.SetUID || f.SetGID +} + +// DropSetUIDAndMaybeGID turns off setuid, and turns off setgid if f allows +// group execution. +func (f *FilePermissions) DropSetUIDAndMaybeGID() { + f.SetUID = false + if f.Group.Execute { + f.SetGID = false + } +} + // FileOwner represents ownership of a file. // // +stateify savable diff --git a/pkg/sentry/fs/dev/dev.go b/pkg/sentry/fs/dev/dev.go index e84ba7a5d..c62effd52 100644 --- a/pkg/sentry/fs/dev/dev.go +++ b/pkg/sentry/fs/dev/dev.go @@ -16,6 +16,7 @@ package dev import ( + "fmt" "math" "gvisor.dev/gvisor/pkg/context" @@ -90,6 +91,11 @@ func newSymlink(ctx context.Context, target string, msrc *fs.MountSource) *fs.In // New returns the root node of a device filesystem. func New(ctx context.Context, msrc *fs.MountSource) *fs.Inode { + shm, err := tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc, nil /* parent */) + if err != nil { + panic(fmt.Sprintf("tmpfs.NewDir failed: %v", err)) + } + contents := map[string]*fs.Inode{ "fd": newSymlink(ctx, "/proc/self/fd", msrc), "stdin": newSymlink(ctx, "/proc/self/fd/0", msrc), @@ -108,7 +114,7 @@ func New(ctx context.Context, msrc *fs.MountSource) *fs.Inode { "random": newMemDevice(ctx, newRandomDevice(ctx, fs.RootOwner, 0444), msrc, randomDevMinor), "urandom": newMemDevice(ctx, newRandomDevice(ctx, fs.RootOwner, 0444), msrc, urandomDevMinor), - "shm": tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc), + "shm": shm, // A devpts is typically mounted at /dev/pts to provide // pseudoterminal support. Place an empty directory there for diff --git a/pkg/sentry/fs/fsutil/host_mappable.go b/pkg/sentry/fs/fsutil/host_mappable.go index e1e38b498..8ac3738e9 100644 --- a/pkg/sentry/fs/fsutil/host_mappable.go +++ b/pkg/sentry/fs/fsutil/host_mappable.go @@ -155,12 +155,20 @@ func (h *HostMappable) DecRef(fr memmap.FileRange) { // T2: Appends to file causing it to grow // T2: Writes to mapped pages and COW happens // T1: Continues and wronly invalidates the page mapped in step above. -func (h *HostMappable) Truncate(ctx context.Context, newSize int64) error { +func (h *HostMappable) Truncate(ctx context.Context, newSize int64, uattr fs.UnstableAttr) error { h.truncateMu.Lock() defer h.truncateMu.Unlock() mask := fs.AttrMask{Size: true} attr := fs.UnstableAttr{Size: newSize} + + // Truncating a file clears privilege bits. + if uattr.Perms.HasSetUIDOrGID() { + mask.Perms = true + attr.Perms = uattr.Perms + attr.Perms.DropSetUIDAndMaybeGID() + } + if err := h.backingFile.SetMaskedAttributes(ctx, mask, attr, false); err != nil { return err } @@ -193,10 +201,17 @@ func (h *HostMappable) Allocate(ctx context.Context, offset int64, length int64) } // Write writes to the file backing this mappable. -func (h *HostMappable) Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) { +func (h *HostMappable) Write(ctx context.Context, src usermem.IOSequence, offset int64, uattr fs.UnstableAttr) (int64, error) { h.truncateMu.RLock() + defer h.truncateMu.RUnlock() n, err := src.CopyInTo(ctx, &writer{ctx: ctx, hostMappable: h, off: offset}) - h.truncateMu.RUnlock() + if n > 0 && uattr.Perms.HasSetUIDOrGID() { + mask := fs.AttrMask{Perms: true} + uattr.Perms.DropSetUIDAndMaybeGID() + if err := h.backingFile.SetMaskedAttributes(ctx, mask, uattr, false); err != nil { + return n, err + } + } return n, err } diff --git a/pkg/sentry/fs/fsutil/inode_cached.go b/pkg/sentry/fs/fsutil/inode_cached.go index 7856b354b..855029b84 100644 --- a/pkg/sentry/fs/fsutil/inode_cached.go +++ b/pkg/sentry/fs/fsutil/inode_cached.go @@ -310,6 +310,12 @@ func (c *CachingInodeOperations) Truncate(ctx context.Context, inode *fs.Inode, now := ktime.NowFromContext(ctx) masked := fs.AttrMask{Size: true} attr := fs.UnstableAttr{Size: size} + if c.attr.Perms.HasSetUIDOrGID() { + masked.Perms = true + attr.Perms = c.attr.Perms + attr.Perms.DropSetUIDAndMaybeGID() + c.attr.Perms = attr.Perms + } if err := c.backingFile.SetMaskedAttributes(ctx, masked, attr, false); err != nil { c.dataMu.Unlock() return err @@ -685,13 +691,14 @@ func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) { return done, nil } -// maybeGrowFile grows the file's size if data has been written past the old -// size. +// maybeUpdateAttrs updates the file's attributes after a write. It updates +// size if data has been written past the old size, and setuid/setgid if any +// bytes were written. // // Preconditions: // * rw.c.attrMu must be locked. // * rw.c.dataMu must be locked. -func (rw *inodeReadWriter) maybeGrowFile() { +func (rw *inodeReadWriter) maybeUpdateAttrs(nwritten uint64) { // If the write ends beyond the file's previous size, it causes the // file to grow. if rw.offset > rw.c.attr.Size { @@ -705,6 +712,12 @@ func (rw *inodeReadWriter) maybeGrowFile() { rw.c.attr.Usage = rw.offset rw.c.dirtyAttr.Usage = true } + + // If bytes were written, ensure setuid and setgid are cleared. + if nwritten > 0 && rw.c.attr.Perms.HasSetUIDOrGID() { + rw.c.dirtyAttr.Perms = true + rw.c.attr.Perms.DropSetUIDAndMaybeGID() + } } // WriteFromBlocks implements safemem.Writer.WriteFromBlocks. @@ -732,7 +745,7 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error segMR := seg.Range().Intersect(mr) ims, err := mf.MapInternal(seg.FileRangeOf(segMR), hostarch.Write) if err != nil { - rw.maybeGrowFile() + rw.maybeUpdateAttrs(done) rw.c.dataMu.Unlock() return done, err } @@ -744,7 +757,7 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error srcs = srcs.DropFirst64(n) rw.c.dirty.MarkDirty(segMR) if err != nil { - rw.maybeGrowFile() + rw.maybeUpdateAttrs(done) rw.c.dataMu.Unlock() return done, err } @@ -765,7 +778,7 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error srcs = srcs.DropFirst64(n) // Partial writes are fine. But we must stop writing. if n != src.NumBytes() || err != nil { - rw.maybeGrowFile() + rw.maybeUpdateAttrs(done) rw.c.dataMu.Unlock() return done, err } @@ -774,7 +787,7 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error seg, gap = gap.NextSegment(), FileRangeGapIterator{} } } - rw.maybeGrowFile() + rw.maybeUpdateAttrs(done) rw.c.dataMu.Unlock() return done, nil } diff --git a/pkg/sentry/fs/gofer/file.go b/pkg/sentry/fs/gofer/file.go index 819e140bc..73d80d9b5 100644 --- a/pkg/sentry/fs/gofer/file.go +++ b/pkg/sentry/fs/gofer/file.go @@ -237,10 +237,20 @@ func (f *fileOperations) Write(ctx context.Context, file *fs.File, src usermem.I // and availability of a host-mappable FD. if f.inodeOperations.session().cachePolicy.useCachingInodeOps(file.Dirent.Inode) { n, err = f.inodeOperations.cachingInodeOps.Write(ctx, src, offset) - } else if f.inodeOperations.fileState.hostMappable != nil { - n, err = f.inodeOperations.fileState.hostMappable.Write(ctx, src, offset) } else { - n, err = src.CopyInTo(ctx, f.handles.readWriterAt(ctx, offset)) + uattr, e := f.UnstableAttr(ctx, file) + if e != nil { + return 0, e + } + if f.inodeOperations.fileState.hostMappable != nil { + n, err = f.inodeOperations.fileState.hostMappable.Write(ctx, src, offset, uattr) + } else { + n, err = src.CopyInTo(ctx, f.handles.readWriterAt(ctx, offset)) + if n > 0 && uattr.Perms.HasSetUIDOrGID() { + uattr.Perms.DropSetUIDAndMaybeGID() + f.inodeOperations.SetPermissions(ctx, file.Dirent.Inode, uattr.Perms) + } + } } if n == 0 { diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go index b97635ec4..da3178527 100644 --- a/pkg/sentry/fs/gofer/inode.go +++ b/pkg/sentry/fs/gofer/inode.go @@ -600,11 +600,25 @@ func (i *inodeOperations) Truncate(ctx context.Context, inode *fs.Inode, length if i.session().cachePolicy.useCachingInodeOps(inode) { return i.cachingInodeOps.Truncate(ctx, inode, length) } + + uattr, err := i.fileState.unstableAttr(ctx) + if err != nil { + return err + } + if i.session().cachePolicy == cacheRemoteRevalidating { - return i.fileState.hostMappable.Truncate(ctx, length) + return i.fileState.hostMappable.Truncate(ctx, length, uattr) + } + + mask := p9.SetAttrMask{Size: true} + attr := p9.SetAttr{Size: uint64(length)} + if uattr.Perms.HasSetUIDOrGID() { + mask.Permissions = true + uattr.Perms.DropSetUIDAndMaybeGID() + attr.Permissions = p9.FileMode(uattr.Perms.LinuxMode()) } - return i.fileState.file.setAttr(ctx, p9.SetAttrMask{Size: true}, p9.SetAttr{Size: uint64(length)}) + return i.fileState.file.setAttr(ctx, mask, attr) } // GetXattr implements fs.InodeOperations.GetXattr. diff --git a/pkg/sentry/fs/gofer/path.go b/pkg/sentry/fs/gofer/path.go index 6b3627813..940838a44 100644 --- a/pkg/sentry/fs/gofer/path.go +++ b/pkg/sentry/fs/gofer/path.go @@ -130,7 +130,16 @@ func (i *inodeOperations) Create(ctx context.Context, dir *fs.Inode, name string panic(fmt.Sprintf("Create called with unknown or unset open flags: %v", flags)) } + // If the parent directory has setgid enabled, change the new file's owner. owner := fs.FileOwnerFromContext(ctx) + parentUattr, err := dir.UnstableAttr(ctx) + if err != nil { + return nil, err + } + if parentUattr.Perms.SetGID { + owner.GID = parentUattr.Owner.GID + } + hostFile, err := newFile.create(ctx, name, openFlags, p9.FileMode(perm.LinuxMode()), p9.UID(owner.UID), p9.GID(owner.GID)) if err != nil { // Could not create the file. @@ -225,7 +234,18 @@ func (i *inodeOperations) CreateDirectory(ctx context.Context, dir *fs.Inode, s return syserror.ENAMETOOLONG } + // If the parent directory has setgid enabled, change the new directory's + // owner and enable setgid. owner := fs.FileOwnerFromContext(ctx) + parentUattr, err := dir.UnstableAttr(ctx) + if err != nil { + return err + } + if parentUattr.Perms.SetGID { + owner.GID = parentUattr.Owner.GID + perm.SetGID = true + } + if _, err := i.fileState.file.mkdir(ctx, s, p9.FileMode(perm.LinuxMode()), p9.UID(owner.UID), p9.GID(owner.GID)); err != nil { return err } diff --git a/pkg/sentry/fs/tmpfs/fs.go b/pkg/sentry/fs/tmpfs/fs.go index bc117ca6a..b48d475ed 100644 --- a/pkg/sentry/fs/tmpfs/fs.go +++ b/pkg/sentry/fs/tmpfs/fs.go @@ -151,5 +151,5 @@ func (f *Filesystem) Mount(ctx context.Context, device string, flags fs.MountSou } // Construct the tmpfs root. - return NewDir(ctx, nil, owner, perms, msrc), nil + return NewDir(ctx, nil, owner, perms, msrc, nil /* parent */) } diff --git a/pkg/sentry/fs/tmpfs/inode_file.go b/pkg/sentry/fs/tmpfs/inode_file.go index f4de8c968..7faa822f0 100644 --- a/pkg/sentry/fs/tmpfs/inode_file.go +++ b/pkg/sentry/fs/tmpfs/inode_file.go @@ -226,6 +226,12 @@ func (f *fileInodeOperations) Truncate(ctx context.Context, _ *fs.Inode, size in now := ktime.NowFromContext(ctx) f.attr.ModificationTime = now f.attr.StatusChangeTime = now + + // Truncating clears privilege bits. + f.attr.Perms.SetUID = false + if f.attr.Perms.Group.Execute { + f.attr.Perms.SetGID = false + } } f.dataMu.Unlock() @@ -363,7 +369,14 @@ func (f *fileInodeOperations) write(ctx context.Context, src usermem.IOSequence, now := ktime.NowFromContext(ctx) f.attr.ModificationTime = now f.attr.StatusChangeTime = now - return src.CopyInTo(ctx, &fileReadWriter{f, offset}) + nwritten, err := src.CopyInTo(ctx, &fileReadWriter{f, offset}) + + // Writing clears privilege bits. + if nwritten > 0 { + f.attr.Perms.DropSetUIDAndMaybeGID() + } + + return nwritten, err } type fileReadWriter struct { diff --git a/pkg/sentry/fs/tmpfs/tmpfs.go b/pkg/sentry/fs/tmpfs/tmpfs.go index 577052888..6aa8ff331 100644 --- a/pkg/sentry/fs/tmpfs/tmpfs.go +++ b/pkg/sentry/fs/tmpfs/tmpfs.go @@ -87,7 +87,20 @@ type Dir struct { var _ fs.InodeOperations = (*Dir)(nil) // NewDir returns a new directory. -func NewDir(ctx context.Context, contents map[string]*fs.Inode, owner fs.FileOwner, perms fs.FilePermissions, msrc *fs.MountSource) *fs.Inode { +func NewDir(ctx context.Context, contents map[string]*fs.Inode, owner fs.FileOwner, perms fs.FilePermissions, msrc *fs.MountSource, parent *fs.Inode) (*fs.Inode, error) { + // If the parent has setgid enabled, the new directory enables it and changes + // its GID. + if parent != nil { + parentUattr, err := parent.UnstableAttr(ctx) + if err != nil { + return nil, err + } + if parentUattr.Perms.SetGID { + owner.GID = parentUattr.Owner.GID + perms.SetGID = true + } + } + d := &Dir{ ramfsDir: ramfs.NewDir(ctx, contents, owner, perms), kernel: kernel.KernelFromContext(ctx), @@ -101,7 +114,7 @@ func NewDir(ctx context.Context, contents map[string]*fs.Inode, owner fs.FileOwn InodeID: tmpfsDevice.NextIno(), BlockSize: hostarch.PageSize, Type: fs.Directory, - }) + }), nil } // afterLoad is invoked by stateify. @@ -219,11 +232,21 @@ func (d *Dir) SetTimestamps(ctx context.Context, i *fs.Inode, ts fs.TimeSpec) er func (d *Dir) newCreateOps() *ramfs.CreateOps { return &ramfs.CreateOps{ NewDir: func(ctx context.Context, dir *fs.Inode, perms fs.FilePermissions) (*fs.Inode, error) { - return NewDir(ctx, nil, fs.FileOwnerFromContext(ctx), perms, dir.MountSource), nil + return NewDir(ctx, nil, fs.FileOwnerFromContext(ctx), perms, dir.MountSource, dir) }, NewFile: func(ctx context.Context, dir *fs.Inode, perms fs.FilePermissions) (*fs.Inode, error) { + // If the parent has setgid enabled, change the GID of the new file. + owner := fs.FileOwnerFromContext(ctx) + parentUattr, err := dir.UnstableAttr(ctx) + if err != nil { + return nil, err + } + if parentUattr.Perms.SetGID { + owner.GID = parentUattr.Owner.GID + } + uattr := fs.WithCurrentTime(ctx, fs.UnstableAttr{ - Owner: fs.FileOwnerFromContext(ctx), + Owner: owner, Perms: perms, // Always start unlinked. Links: 0, diff --git a/pkg/sentry/fs/user/user_test.go b/pkg/sentry/fs/user/user_test.go index 12b786224..7f8fa8038 100644 --- a/pkg/sentry/fs/user/user_test.go +++ b/pkg/sentry/fs/user/user_test.go @@ -104,7 +104,10 @@ func TestGetExecUserHome(t *testing.T) { t.Run(name, func(t *testing.T) { ctx := contexttest.Context(t) msrc := fs.NewPseudoMountSource(ctx) - rootInode := tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc) + rootInode, err := tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc, nil /* parent */) + if err != nil { + t.Fatalf("tmpfs.NewDir failed: %v", err) + } mns, err := fs.NewMountNamespace(ctx, rootInode) if err != nil { diff --git a/pkg/sentry/fsimpl/overlay/regular_file.go b/pkg/sentry/fsimpl/overlay/regular_file.go index 43bfd69a3..82491a0f8 100644 --- a/pkg/sentry/fsimpl/overlay/regular_file.go +++ b/pkg/sentry/fsimpl/overlay/regular_file.go @@ -207,9 +207,10 @@ func (fd *regularFileFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) e return err } - // Changing owners may clear one or both of the setuid and setgid bits, - // so we may have to update opts before setting d.mode. - if opts.Stat.Mask&(linux.STATX_UID|linux.STATX_GID) != 0 { + // Changing owners or truncating may clear one or both of the setuid and + // setgid bits, so we may have to update opts before setting d.mode. + inotifyMask := opts.Stat.Mask + if opts.Stat.Mask&(linux.STATX_UID|linux.STATX_GID|linux.STATX_SIZE) != 0 { stat, err := wrappedFD.Stat(ctx, vfs.StatOptions{ Mask: linux.STATX_MODE, }) @@ -218,10 +219,14 @@ func (fd *regularFileFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) e } opts.Stat.Mode = stat.Mode opts.Stat.Mask |= linux.STATX_MODE + // Don't generate inotify IN_ATTRIB for size-only changes (truncations). + if opts.Stat.Mask&(linux.STATX_UID|linux.STATX_GID) != 0 { + inotifyMask |= linux.STATX_MODE + } } d.updateAfterSetStatLocked(&opts) - if ev := vfs.InotifyEventFromStatMask(opts.Stat.Mask); ev != 0 { + if ev := vfs.InotifyEventFromStatMask(inotifyMask); ev != 0 { d.InotifyWithParent(ctx, ev, 0, vfs.InodeEvent) } return nil diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go index 9cd238efd..37443ab78 100644 --- a/pkg/sentry/syscalls/linux/sys_file.go +++ b/pkg/sentry/syscalls/linux/sys_file.go @@ -1673,9 +1673,11 @@ func chown(t *kernel.Task, d *fs.Dirent, uid auth.UID, gid auth.GID) error { if err != nil { return err } + c := t.Credentials() hasCap := d.Inode.CheckCapability(t, linux.CAP_CHOWN) isOwner := uattr.Owner.UID == c.EffectiveKUID + var clearPrivilege bool if uid.Ok() { kuid := c.UserNamespace.MapToKUID(uid) // Valid UID must be supplied if UID is to be changed. @@ -1693,6 +1695,11 @@ func chown(t *kernel.Task, d *fs.Dirent, uid auth.UID, gid auth.GID) error { return syserror.EPERM } + // The setuid and setgid bits are cleared during a chown. + if uattr.Owner.UID != kuid { + clearPrivilege = true + } + owner.UID = kuid } if gid.Ok() { @@ -1711,6 +1718,11 @@ func chown(t *kernel.Task, d *fs.Dirent, uid auth.UID, gid auth.GID) error { return syserror.EPERM } + // The setuid and setgid bits are cleared during a chown. + if uattr.Owner.GID != kgid { + clearPrivilege = true + } + owner.GID = kgid } @@ -1721,10 +1733,14 @@ func chown(t *kernel.Task, d *fs.Dirent, uid auth.UID, gid auth.GID) error { if err := d.Inode.SetOwner(t, d, owner); err != nil { return err } + // Clear privilege bits if needed and they are set. + if clearPrivilege && uattr.Perms.HasSetUIDOrGID() && !fs.IsDir(d.Inode.StableAttr) { + uattr.Perms.DropSetUIDAndMaybeGID() + if !d.Inode.SetPermissions(t, d, uattr.Perms) { + return syserror.EPERM + } + } - // When the owner or group are changed by an unprivileged user, - // chown(2) also clears the set-user-ID and set-group-ID bits, but - // we do not support them. return nil } |