CVE-2026-90318: fallo en Linux

In the Linux kernel, the following vulnerability has been resolved: fat: release buffer head after rebuilding parent fat_scan_logstart() leaves the matching directory entry's buffer head in sinfo.bh for the caller to release, just like fat_scan(). fat_rebuild_parent() uses the directory entry to rebuild the parent inode for the nostale_ro NFS export path, but does not release sinfo.bh after a successful scan. Release it once fat_build_inode() has consumed the directory entry data.