diff options
Diffstat (limited to 'pkg/sentry/fsimpl/gofer/regular_file.go')
| -rw-r--r-- | pkg/sentry/fsimpl/gofer/regular_file.go | 41 |
1 files changed, 34 insertions, 7 deletions
diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go index f10350c97..02317a133 100644 --- a/pkg/sentry/fsimpl/gofer/regular_file.go +++ b/pkg/sentry/fsimpl/gofer/regular_file.go @@ -155,26 +155,53 @@ func (fd *regularFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts // PWrite implements vfs.FileDescriptionImpl.PWrite. func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) { + n, _, err := fd.pwrite(ctx, src, offset, opts) + return n, err +} + +// pwrite returns the number of bytes written, final offset, error. The final +// offset should be ignored by PWrite. +func (fd *regularFileFD) pwrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (written, finalOff int64, err error) { if offset < 0 { - return 0, syserror.EINVAL + return 0, offset, syserror.EINVAL } // Check that flags are supported. // // TODO(gvisor.dev/issue/2601): Support select pwritev2 flags. if opts.Flags&^linux.RWF_HIPRI != 0 { - return 0, syserror.EOPNOTSUPP + return 0, offset, syserror.EOPNOTSUPP + } + + d := fd.dentry() + // If the fd was opened with O_APPEND, make sure the file size is updated. + // There is a possible race here if size is modified externally after + // metadata cache is updated. + if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 && !d.cachedMetadataAuthoritative() { + if err := d.updateFromGetattr(ctx); err != nil { + return 0, offset, err + } } + d.metadataMu.Lock() + defer d.metadataMu.Unlock() + // Set offset to file size if the fd was opened with O_APPEND. + if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 { + // Holding d.metadataMu is sufficient for reading d.size. + offset = int64(d.size) + } limit, err := vfs.CheckLimit(ctx, offset, src.NumBytes()) if err != nil { - return 0, err + return 0, offset, err } src = src.TakeFirst64(limit) + n, err := fd.pwriteLocked(ctx, src, offset, opts) + return n, offset + n, err +} +// Preconditions: fd.dentry().metatdataMu must be locked. +func (fd *regularFileFD) pwriteLocked(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) { d := fd.dentry() - d.metadataMu.Lock() - defer d.metadataMu.Unlock() if d.fs.opts.interop != InteropModeShared { // Compare Linux's mm/filemap.c:__generic_file_write_iter() => // file_update_time(). This is d.touchCMtime(), but without locking @@ -237,8 +264,8 @@ func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off // Write implements vfs.FileDescriptionImpl.Write. func (fd *regularFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) { fd.mu.Lock() - n, err := fd.PWrite(ctx, src, fd.off, opts) - fd.off += n + n, off, err := fd.pwrite(ctx, src, fd.off, opts) + fd.off = off fd.mu.Unlock() return n, err } |