Miscellaneous VFS2 fixes.

PiperOrigin-RevId: 316627764

1 files changed, 16 insertions, 10 deletions

diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 0d88a328e..ac051b3a7 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -835,6 +835,14 @@ func (d *dentry) statTo(stat *linux.Statx) {
 	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME | linux.STATX_INO | linux.STATX_SIZE | linux.STATX_BLOCKS | linux.STATX_BTIME
 	stat.Blksize = atomic.LoadUint32(&d.blockSize)
 	stat.Nlink = atomic.LoadUint32(&d.nlink)
+	if stat.Nlink == 0 {
+		// The remote filesystem doesn't support link count; just make
+		// something up. This is consistent with Linux, where
+		// fs/inode.c:inode_init_always() initializes link count to 1, and
+		// fs/9p/vfs_inode_dotl.c:v9fs_stat2inode_dotl() doesn't touch it if
+		// it's not provided by the remote filesystem.
+		stat.Nlink = 1
+	}
 	stat.UID = atomic.LoadUint32(&d.uid)
 	stat.GID = atomic.LoadUint32(&d.gid)
 	stat.Mode = uint16(atomic.LoadUint32(&d.mode))
@@ -1346,23 +1354,21 @@ func (d *dentry) ensureSharedHandle(ctx context.Context, read, write, trunc bool
 }
 
 // incLinks increments link count.
-//
-// Preconditions: d.nlink != 0 && d.nlink < math.MaxUint32.
 func (d *dentry) incLinks() {
-	v := atomic.AddUint32(&d.nlink, 1)
-	if v < 2 {
-		panic(fmt.Sprintf("dentry.nlink is invalid (was 0 or overflowed): %d", v))
+	if atomic.LoadUint32(&d.nlink) == 0 {
+		// The remote filesystem doesn't support link count.
+		return
 	}
+	atomic.AddUint32(&d.nlink, 1)
 }
 
 // decLinks decrements link count.
-//
-// Preconditions: d.nlink > 1.
 func (d *dentry) decLinks() {
-	v := atomic.AddUint32(&d.nlink, ^uint32(0))
-	if v == 0 {
-		panic(fmt.Sprintf("dentry.nlink must be greater than 0: %d", v))
+	if atomic.LoadUint32(&d.nlink) == 0 {
+		// The remote filesystem doesn't support link count.
+		return
 	}
+	atomic.AddUint32(&d.nlink, ^uint32(0))
 }
 
 // fileDescription is embedded by gofer implementations of