diff options
author | Ayush Ranjan <ayushranjan@google.com> | 2020-08-18 21:55:16 -0700 |
---|---|---|
committer | Rahat Mahmood <46939889+mrahatm@users.noreply.github.com> | 2020-08-19 11:38:34 -0700 |
commit | 01098ad9a23c01bbbd3f8d60242646f88dd42040 (patch) | |
tree | 0a9f7d8dae70e5f3e3f67fdb745787988d04ace9 /pkg | |
parent | ab98a35a9adb2df0359478b8898e78337e2d0392 (diff) |
[vfs] Allow offsets for special files other than regular files.
Some character and block devices can be seekable. So allow their FD to maintain
file offset.
PiperOrigin-RevId: 327370684
Diffstat (limited to 'pkg')
-rw-r--r-- | pkg/sentry/fsimpl/gofer/special_file.go | 35 |
1 files changed, 22 insertions, 13 deletions
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go index a6368fdd0..3c39aa9b7 100644 --- a/pkg/sentry/fsimpl/gofer/special_file.go +++ b/pkg/sentry/fsimpl/gofer/special_file.go @@ -39,8 +39,14 @@ type specialFileFD struct { // handle is used for file I/O. handle is immutable. handle handle + // isRegularFile is true if this FD represents a regular file which is only + // possible when filesystemOptions.regularFilesUseSpecialFileFD is in + // effect. isRegularFile is immutable. + isRegularFile bool + // seekable is true if this file description represents a file for which - // file offset is significant, i.e. a regular file. seekable is immutable. + // file offset is significant, i.e. a regular file, character device or + // block device. seekable is immutable. seekable bool // haveQueue is true if this file description represents a file for which @@ -55,12 +61,13 @@ type specialFileFD struct { func newSpecialFileFD(h handle, mnt *vfs.Mount, d *dentry, locks *vfs.FileLocks, flags uint32) (*specialFileFD, error) { ftype := d.fileType() - seekable := ftype == linux.S_IFREG + seekable := ftype == linux.S_IFREG || ftype == linux.S_IFCHR || ftype == linux.S_IFBLK haveQueue := (ftype == linux.S_IFIFO || ftype == linux.S_IFSOCK) && h.fd >= 0 fd := &specialFileFD{ - handle: h, - seekable: seekable, - haveQueue: haveQueue, + handle: h, + isRegularFile: ftype == linux.S_IFREG, + seekable: seekable, + haveQueue: haveQueue, } fd.LockFD.Init(locks) if haveQueue { @@ -200,13 +207,13 @@ func (fd *specialFileFD) pwrite(ctx context.Context, src usermem.IOSequence, off // If the regular file 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.seekable && fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 && !d.cachedMetadataAuthoritative() { + if fd.isRegularFile && fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 && !d.cachedMetadataAuthoritative() { if err := d.updateFromGetattr(ctx); err != nil { return 0, offset, err } } - if fd.seekable { + if fd.isRegularFile { // We need to hold the metadataMu *while* writing to a regular file. d.metadataMu.Lock() defer d.metadataMu.Unlock() @@ -236,18 +243,20 @@ func (fd *specialFileFD) pwrite(ctx context.Context, src usermem.IOSequence, off if err == syserror.EAGAIN { err = syserror.ErrWouldBlock } - finalOff = offset + // Update offset if the offset is valid. + if offset >= 0 { + offset += int64(n) + } // Update file size for regular files. - if fd.seekable { - finalOff += int64(n) + if fd.isRegularFile { // d.metadataMu is already locked at this point. - if uint64(finalOff) > d.size { + if uint64(offset) > d.size { d.dataMu.Lock() defer d.dataMu.Unlock() - atomic.StoreUint64(&d.size, uint64(finalOff)) + atomic.StoreUint64(&d.size, uint64(offset)) } } - return int64(n), finalOff, err + return int64(n), offset, err } // Write implements vfs.FileDescriptionImpl.Write. |