CVE-2026-97594landlock: Fix use-after-free of the source's parent directory

Official description

In the Linux kernel, the following vulnerability has been resolved: landlock: Fix use-after-free of the source's parent directory current_check_refer_path() reads old_dentry->d_parent without holding a reference nor a lock on it, and then dereferences it in collect_domain_accesses() and in the audit record. A reference on a child does not pin its parent: __d_move() reassigns dentry->d_parent and drops the reference the child held on its former parent. hook_path_rename() is not affected because the rename path calls lock_rename() before the hook, so the source cannot be reparented under it. hook_path_link() has no such protection: filename_linkat() holds a reference on the source dentry but neither locks nor references its parent, so a concurrent rename(2) can reparent the source while security_path_link() runs, and the former parent can then be removed and freed while the hook walks it. A process can trigger this after entering a Landlock domain that handles at least one filesystem access right. The process can then race a linkat(2) loop against rename(2) and rmdir(2): BUG: KASAN: slab-use-after-free in collect_domain_accesses+0x278/0x290 Read of size 4 at addr ffff888160bd53f4 by task llrepro2/549 collect_domain_accesses+0x278/0x290 current_check_refer_path+0x952/0x1120 security_path_link+0x1be/0x320 filename_linkat+0x342/0x6d0 __x64_sys_linkat+0xfa/0x150 Freed by task 562: kmem_cache_free+0x139/0x4c0 i_callback+0x4b/0x80 rcu_core+0x7dc/0x10a0 Take a reference on the dentry selected as the source parent, using dget() for the common-mount-root case and dget_parent() otherwise. Release it after the hierarchy walk and synchronous audit logging. [mic: Clarify the caller, reachability, and reference handling]

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/0475440ff8c04be26a88733af0c85f597bb28c0a
• https://git.kernel.org/stable/c/48fc1c74052c956c59d5b16b5e18e0dd36b76aa2
• https://git.kernel.org/stable/c/4c37992b9668c4f37aae41dd95c369f7b6009915
• https://git.kernel.org/stable/c/379efd2ce8b26fd35feb13ccc2f671ff105a5052
• https://git.kernel.org/stable/c/ba29c46ccfe3ebadfb8aa18149186c49f84b14f8
• https://git.kernel.org/stable/c/2c6dc792538260a8087ac5b22c31b3b8e47c85d6