CVE-2026-63817

In the Linux kernel, the following vulnerability has been resolved:

f2fs: validate compress cache inode only when enabled

F2FS_COMPRESS_INO() uses NM_I(sbi)->max_nid as the synthetic inode

number for the compressed page cache inode. That inode only exists when

the compress_cache mount option is enabled.

When compress_cache is disabled, max_nid is outside the valid inode

range. A corrupted directory entry that points to ino == max_nid should

therefore be rejected by f2fs_check_nid_range(). However, is_meta_ino()

currently treats F2FS_COMPRESS_INO() as a meta inode unconditionally,

so f2fs_iget() bypasses do_read_inode() and its nid range check, and

instantiates a fake internal inode instead.

Gate the compressed cache inode case on COMPRESS_CACHE, matching

f2fs_init_compress_inode(). With compress_cache disabled, ino ==

max_nid now follows the normal inode path and is rejected as an

out-of-range nid.