diff options
| -rw-r--r-- | pkg/sentry/fsimpl/gofer/gofer.go | 24 | ||||
| -rw-r--r-- | pkg/sentry/fsimpl/gofer/regular_file.go | 4 |
2 files changed, 18 insertions, 10 deletions
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go index 2b83094cd..b74d489a0 100644 --- a/pkg/sentry/fsimpl/gofer/gofer.go +++ b/pkg/sentry/fsimpl/gofer/gofer.go @@ -602,8 +602,14 @@ type dentry struct { // returned by the server. dirents is protected by dirMu. dirents []vfs.Dirent - // Cached metadata; protected by metadataMu and accessed using atomic - // memory operations unless otherwise specified. + // Cached metadata; protected by metadataMu. + // To access: + // - In situations where consistency is not required (like stat), these + // can be accessed using atomic operations only (without locking). + // - Lock metadataMu and can access without atomic operations. + // To mutate: + // - Lock metadataMu and use atomic operations to update because we might + // have atomic readers that don't hold the lock. metadataMu sync.Mutex ino inodeNumber // immutable mode uint32 // type is immutable, perms are mutable @@ -616,7 +622,7 @@ type dentry struct { ctime int64 btime int64 // File size, protected by both metadataMu and dataMu (i.e. both must be - // locked to mutate it). + // locked to mutate it; locking either is sufficient to access it). size uint64 // nlink counts the number of hard links to this dentry. It's updated and @@ -904,14 +910,14 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, stat *lin // Prepare for truncate. if stat.Mask&linux.STATX_SIZE != 0 { - switch d.mode & linux.S_IFMT { - case linux.S_IFREG: + switch mode.FileType() { + case linux.ModeRegular: if !setLocalMtime { // Truncate updates mtime. setLocalMtime = true stat.Mtime.Nsec = linux.UTIME_NOW } - case linux.S_IFDIR: + case linux.ModeDirectory: return syserror.EISDIR default: return syserror.EINVAL @@ -994,7 +1000,7 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, stat *lin func (d *dentry) updateFileSizeLocked(newSize uint64) { d.dataMu.Lock() oldSize := d.size - d.size = newSize + atomic.StoreUint64(&d.size, newSize) // d.dataMu must be unlocked to lock d.mapsMu and invalidate mappings // below. This allows concurrent calls to Read/Translate/etc. These // functions synchronize with truncation by refusing to use cache @@ -1340,8 +1346,8 @@ func (d *dentry) removexattr(ctx context.Context, creds *auth.Credentials, name // Extended attributes in the user.* namespace are only supported for regular // files and directories. func (d *dentry) userXattrSupported() bool { - filetype := linux.S_IFMT & atomic.LoadUint32(&d.mode) - return filetype == linux.S_IFREG || filetype == linux.S_IFDIR + filetype := linux.FileMode(atomic.LoadUint32(&d.mode)).FileType() + return filetype == linux.ModeRegular || filetype == linux.ModeDirectory } // Preconditions: !d.isSynthetic(). d.isRegularFile() || d.isDir(). diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go index a2f02d9c7..f10350c97 100644 --- a/pkg/sentry/fsimpl/gofer/regular_file.go +++ b/pkg/sentry/fsimpl/gofer/regular_file.go @@ -89,7 +89,9 @@ func (fd *regularFileFD) Allocate(ctx context.Context, mode, offset, length uint if err != nil { return err } - d.size = size + d.dataMu.Lock() + atomic.StoreUint64(&d.size, size) + d.dataMu.Unlock() if !d.cachedMetadataAuthoritative() { d.touchCMtimeLocked() } |