diff options
| -rwxr-xr-x | pkg/sentry/kernel/pipe/vfs.go | 12 | ||||
| -rwxr-xr-x | pkg/sentry/vfs/file_description.go | 66 | ||||
| -rwxr-xr-x | pkg/sentry/vfs/permissions.go | 5 |
3 files changed, 67 insertions, 16 deletions
diff --git a/pkg/sentry/kernel/pipe/vfs.go b/pkg/sentry/kernel/pipe/vfs.go index bf7461cbb..6f83e3cee 100755 --- a/pkg/sentry/kernel/pipe/vfs.go +++ b/pkg/sentry/kernel/pipe/vfs.go @@ -66,7 +66,7 @@ func NewVFSPipe(sizeBytes, atomicIOBytes int64) *VFSPipe { // for read and write will succeed both in blocking and nonblocking mode. POSIX // leaves this behavior undefined. This can be used to open a FIFO for writing // while there are no readers available." - fifo(7) -func (vp *VFSPipe) NewVFSPipeFD(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, vfsfd *vfs.FileDescription, flags uint32) (*VFSPipeFD, error) { +func (vp *VFSPipe) NewVFSPipeFD(ctx context.Context, vfsd *vfs.Dentry, vfsfd *vfs.FileDescription, flags uint32) (*VFSPipeFD, error) { vp.mu.Lock() defer vp.mu.Unlock() @@ -76,7 +76,7 @@ func (vp *VFSPipe) NewVFSPipeFD(ctx context.Context, rp *vfs.ResolvingPath, vfsd return nil, syserror.EINVAL } - vfd, err := vp.open(rp, vfsd, vfsfd, flags) + vfd, err := vp.open(vfsd, vfsfd, flags) if err != nil { return nil, err } @@ -118,19 +118,13 @@ func (vp *VFSPipe) NewVFSPipeFD(ctx context.Context, rp *vfs.ResolvingPath, vfsd } // Preconditions: vp.mu must be held. -func (vp *VFSPipe) open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, vfsfd *vfs.FileDescription, flags uint32) (*VFSPipeFD, error) { +func (vp *VFSPipe) open(vfsd *vfs.Dentry, vfsfd *vfs.FileDescription, flags uint32) (*VFSPipeFD, error) { var fd VFSPipeFD fd.flags = flags fd.readable = vfs.MayReadFileWithOpenFlags(flags) fd.writable = vfs.MayWriteFileWithOpenFlags(flags) fd.vfsfd = vfsfd fd.pipe = &vp.pipe - if fd.writable { - // The corresponding Mount.EndWrite() is in VFSPipe.Release(). - if err := rp.Mount().CheckBeginWrite(); err != nil { - return nil, err - } - } switch { case fd.readable && fd.writable: diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go index 6afe280bc..51c95c2d9 100755 --- a/pkg/sentry/vfs/file_description.go +++ b/pkg/sentry/vfs/file_description.go @@ -49,8 +49,23 @@ type FileDescription struct { // A reference is held on vd. vd is immutable. vd VirtualDentry + // opts contains options passed to FileDescription.Init(). opts is + // immutable. opts FileDescriptionOptions + // readable is MayReadFileWithOpenFlags(statusFlags). readable is + // immutable. + // + // readable is analogous to Linux's FMODE_READ. + readable bool + + // writable is MayWriteFileWithOpenFlags(statusFlags). If writable is true, + // the FileDescription holds a write count on vd.mount. writable is + // immutable. + // + // writable is analogous to Linux's FMODE_WRITE. + writable bool + // impl is the FileDescriptionImpl associated with this Filesystem. impl is // immutable. This should be the last field in FileDescription. impl FileDescriptionImpl @@ -77,10 +92,17 @@ type FileDescriptionOptions struct { UseDentryMetadata bool } -// Init must be called before first use of fd. It takes references on mnt and -// d. statusFlags is the initial file description status flags, which is -// usually the full set of flags passed to open(2). -func (fd *FileDescription) Init(impl FileDescriptionImpl, statusFlags uint32, mnt *Mount, d *Dentry, opts *FileDescriptionOptions) { +// Init must be called before first use of fd. If it succeeds, it takes +// references on mnt and d. statusFlags is the initial file description status +// flags, which is usually the full set of flags passed to open(2). +func (fd *FileDescription) Init(impl FileDescriptionImpl, statusFlags uint32, mnt *Mount, d *Dentry, opts *FileDescriptionOptions) error { + writable := MayWriteFileWithOpenFlags(statusFlags) + if writable { + if err := mnt.CheckBeginWrite(); err != nil { + return err + } + } + fd.refs = 1 fd.statusFlags = statusFlags | linux.O_LARGEFILE fd.vd = VirtualDentry{ @@ -89,7 +111,10 @@ func (fd *FileDescription) Init(impl FileDescriptionImpl, statusFlags uint32, mn } fd.vd.IncRef() fd.opts = *opts + fd.readable = MayReadFileWithOpenFlags(statusFlags) + fd.writable = writable fd.impl = impl + return nil } // IncRef increments fd's reference count. @@ -117,6 +142,9 @@ func (fd *FileDescription) TryIncRef() bool { func (fd *FileDescription) DecRef() { if refs := atomic.AddInt64(&fd.refs, -1); refs == 0 { fd.impl.Release() + if fd.writable { + fd.vd.mount.EndWrite() + } fd.vd.DecRef() } else if refs < 0 { panic("FileDescription.DecRef() called without holding a reference") @@ -194,6 +222,16 @@ func (fd *FileDescription) SetStatusFlags(ctx context.Context, creds *auth.Crede return nil } +// IsReadable returns true if fd was opened for reading. +func (fd *FileDescription) IsReadable() bool { + return fd.readable +} + +// IsWritable returns true if fd was opened for writing. +func (fd *FileDescription) IsWritable() bool { + return fd.writable +} + // Impl returns the FileDescriptionImpl associated with fd. func (fd *FileDescription) Impl() FileDescriptionImpl { return fd.impl @@ -241,6 +279,8 @@ type FileDescriptionImpl interface { // Errors: // // - If opts.Flags specifies unsupported options, PRead returns EOPNOTSUPP. + // + // Preconditions: The FileDescription was opened for reading. PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts ReadOptions) (int64, error) // Read is similar to PRead, but does not specify an offset. @@ -254,6 +294,8 @@ type FileDescriptionImpl interface { // Errors: // // - If opts.Flags specifies unsupported options, Read returns EOPNOTSUPP. + // + // Preconditions: The FileDescription was opened for reading. Read(ctx context.Context, dst usermem.IOSequence, opts ReadOptions) (int64, error) // PWrite writes src to the file, starting at the given offset, and returns @@ -268,6 +310,8 @@ type FileDescriptionImpl interface { // // - If opts.Flags specifies unsupported options, PWrite returns // EOPNOTSUPP. + // + // Preconditions: The FileDescription was opened for writing. PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts WriteOptions) (int64, error) // Write is similar to PWrite, but does not specify an offset, which is @@ -281,6 +325,8 @@ type FileDescriptionImpl interface { // Errors: // // - If opts.Flags specifies unsupported options, Write returns EOPNOTSUPP. + // + // Preconditions: The FileDescription was opened for writing. Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) // IterDirents invokes cb on each entry in the directory represented by the @@ -411,11 +457,17 @@ func (fd *FileDescription) StatFS(ctx context.Context) (linux.Statfs, error) { // offset, and returns the number of bytes read. PRead is permitted to return // partial reads with a nil error. func (fd *FileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts ReadOptions) (int64, error) { + if !fd.readable { + return 0, syserror.EBADF + } return fd.impl.PRead(ctx, dst, offset, opts) } // Read is similar to PRead, but does not specify an offset. func (fd *FileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts ReadOptions) (int64, error) { + if !fd.readable { + return 0, syserror.EBADF + } return fd.impl.Read(ctx, dst, opts) } @@ -423,11 +475,17 @@ func (fd *FileDescription) Read(ctx context.Context, dst usermem.IOSequence, opt // offset, and returns the number of bytes written. PWrite is permitted to // return partial writes with a nil error. func (fd *FileDescription) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts WriteOptions) (int64, error) { + if !fd.writable { + return 0, syserror.EBADF + } return fd.impl.PWrite(ctx, src, offset, opts) } // Write is similar to PWrite, but does not specify an offset. func (fd *FileDescription) Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) { + if !fd.writable { + return 0, syserror.EBADF + } return fd.impl.Write(ctx, src, opts) } diff --git a/pkg/sentry/vfs/permissions.go b/pkg/sentry/vfs/permissions.go index d279d05ca..f664581f4 100755 --- a/pkg/sentry/vfs/permissions.go +++ b/pkg/sentry/vfs/permissions.go @@ -94,14 +94,13 @@ func GenericCheckPermissions(creds *auth.Credentials, ats AccessTypes, isDir boo // the set of accesses permitted for the opened file: // // - O_TRUNC causes MayWrite to be set in the returned AccessTypes (since it -// mutates the file), but does not permit the opened to write to the file +// mutates the file), but does not permit writing to the open file description // thereafter. // // - "Linux reserves the special, nonstandard access mode 3 (binary 11) in // flags to mean: check for read and write permission on the file and return a // file descriptor that can't be used for reading or writing." - open(2). Thus -// AccessTypesForOpenFlags returns MayRead|MayWrite in this case, but -// filesystems are responsible for ensuring that access is denied. +// AccessTypesForOpenFlags returns MayRead|MayWrite in this case. // // Use May{Read,Write}FileWithOpenFlags() for these checks instead. func AccessTypesForOpenFlags(flags uint32) AccessTypes { |