CVE-2026-80537

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> xfs: fix off-by-one in rtrefcount btree root level validation<br /> <br /> xfs_rtrefcountbt_compute_maxlevels() sets<br /> <br /> mp-&gt;m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1;<br /> <br /> where the trailing "+ 1" already accounts for the inode-root level, so the<br /> deepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must<br /> satisfy bc_nlevels " instead of "&gt;=", so a<br /> crafted rtreflink (metadir + realtime + reflink) image whose<br /> /rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on<br /> mount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1,<br /> exceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is<br /> sized for exactly bc_maxlevels entries, the first btree op on such a cursor<br /> indexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is<br /> reached by the first rtrefcount cursor built after mount, via log/CoW<br /> recovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an<br /> FS_IOC_GETFSMAP over the realtime device.<br /> <br /> Reject a root level equal to m_rtrefc_maxlevels, matching the "&gt;=" form<br /> already used by the sibling data-device refcount/rmap verifiers and the<br /> in-memory rtrmap verifier.<br /> <br /> BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)<br /> Write of size 2 at addr ffff888018391658 by task exploit/144<br /> xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)<br /> xfs_btree_query_range (fs/xfs/libxfs/xfs_btree.c:5308)<br /> xfs_refcount_recover_cow_leftovers (fs/xfs/libxfs/xfs_refcount.c:2113)<br /> xfs_reflink_recover_cow (fs/xfs/xfs_reflink.c:1085)<br /> xlog_recover_finish (fs/xfs/xfs_log_recover.c:3551)<br /> xfs_mountfs (fs/xfs/xfs_mount.c:1158)<br /> xfs_fs_fill_super (fs/xfs/xfs_super.c:1940)<br /> get_tree_bdev_flags (fs/super.c:1634)<br /> vfs_get_tree (fs/super.c:1694)<br /> path_mount (fs/namespace.c:4161)<br /> __x64_sys_mount (fs/namespace.c:4367)<br /> entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)<br /> The buggy address belongs to the cache xfs_rtrefcountbt_cur of size 216<br /> The buggy address is located 8 bytes to the right of<br /> allocated 216-byte region [ffff888018391578, ffff888018391650)<br /> Kernel panic - not syncing: Fatal exception