ocfs2: rebase copied fsdlm LVB pointers in locking_state

Summary

In the Linux kernel, the following vulnerability has been resolved: ocfs2: rebase copied fsdlm LVB pointers in locking_state The locking_state debugfs iterator snapshots struct ocfs2_lock_res by value under ocfs2_dlm_tracking_lock and later formats that copy in ocfs2_dlm_seq_show(). That is fine for the inline fields, but the userspace fsdlm stack stores the LVB through lksb_fsdlm.sb_lvbptr. Once the iterator drops the tracking lock, a copied non-NULL sb_lvbptr still points into the original lockres owner, so teardown can free that container before the debugfs dump walks the raw LVB bytes. Rebase the copied sb_lvbptr to the copied l_lksb before dumping the raw LVB. The seq snapshot already carries the inline LVB storage reserved in struct ocfs2_dlm_lksb, so the debugfs reader can dump the copied bytes without borrowing the original lockres lifetime. The buggy scenario involves two paths, with each column showing the order within that path: locking_state reader: lockres teardown: 1. ocfs2_dlm_seq_start()/next() 1. file release or another owner copies struct ocfs2_lock_res teardown reaches 2. ocfs2_dlm_seq_show() formats ocfs2_lock_res_free() the copied row 2. the lockres is removed from the 3. ocfs2_dlm_lvb() follows the tracking list copied sb_lvbptr 3. the owner frees the original lockres container Validation reproduced this kernel report: KASAN slab-use-after-free in ocfs2_dlm_seq_show+0x1bd/0x430 RIP: 0033:0x7f8ec4b1e29d The buggy address belongs to the object at ffff88810a1e0800 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 368 bytes inside of freed 1024-byte region [ffff88810a1e0800, ffff88810a1e0c00) Read of size 1 Call trace: dump_stack_lvl+0x66/0xa0 print_report+0xce/0x630 ocfs2_dlm_seq_show+0x1bd/0x430 (fs/ocfs2/dlmglue.c:3137) srso_alias_return_thunk+0x5/0xfbef5 __virt_addr_valid+0x19f/0x330 kasan_report+0xe0/0x110 seq_read_iter+0x29d/0x790 seq_read+0x20a/0x280 find_held_lock+0x2b/0x80 rcu_read_unlock+0x18/0x70 full_proxy_read+0x9e/0xd0 vfs_read+0x12c/0x590 ksys_read+0xd2/0x170 do_user_addr_fault+0x65a/0x890 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task stack: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0xaa/0xb0 ocfs2_file_open+0x13e/0x300 do_dentry_open+0x233/0x7f0 vfs_open+0x5a/0x1b0 path_openat+0x66d/0x1540 do_file_open+0x186/0x2b0 do_sys_openat2+0xce/0x150 __x64_sys_openat+0xd0/0x140 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task stack: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x5f/0x80 kfree+0x313/0x590 ocfs2_file_release+0x138/0x260 __fput+0x1df/0x4b0 fput_close_sync+0xd2/0x170 __x64_sys_close+0x55/0x90 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f