CVE-2024-26987: In the Linux kernel, the following vulnerability has been resolved:  mm/memory-failure: fix deadlock when hugetlb_optimize_vmemmap is enabled  When I did hard offline test with hugetlb pages, below deadlock occurs:  ====================================================== WARNING: possible circular locking dependency detected 6.8.0-11409-gf6cef5f8c37f #1 Not tainted ------------------------------------------------------ bash/46904 is trying to acquire lock: ffffffffabe68910 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_dec+0x16/0x60  but task is already holding lock: ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40  which lock already depends on the new lock.  the existing dependency chain (in reverse order) is:  -> #1 (pcp_batch_high_lock){+.+.}-{3:3}:        __mutex_lock+0x6c/0x770        page_alloc_cpu_online+0x3c/0x70        cpuhp_invoke_callback+0x397/0x5f0        __cpuhp_invoke_callback_range+0x71/0xe0        _cpu_up+0xeb/0x210        cpu_up+0x91/0xe0        cpuhp_bringup_mask+0x49/0xb0        bringup_nonboot_cpus+0xb7/0xe0        smp_init+0x25/0xa0        kernel_init_freeable+0x15f/0x3e0        kernel_init+0x15/0x1b0        ret_from_fork+0x2f/0x50        ret_from_fork_asm+0x1a/0x30  -> #0 (cpu_hotplug_lock){++++}-{0:0}:        __lock_acquire+0x1298/0x1cd0        lock_acquire+0xc0/0x2b0        cpus_read_lock+0x2a/0xc0        static_key_slow_dec+0x16/0x60        __hugetlb_vmemmap_restore_folio+0x1b9/0x200        dissolve_free_huge_page+0x211/0x260        __page_handle_poison+0x45/0xc0        memory_failure+0x65e/0xc70        hard_offline_page_store+0x55/0xa0        kernfs_fop_write_iter+0x12c/0x1d0        vfs_write+0x387/0x550        ksys_write+0x64/0xe0        do_syscall_64+0xca/0x1e0        entry_SYSCALL_64_after_hwframe+0x6d/0x75  other info that might help us debug this:   Possible unsafe locking scenario:         CPU0                    CPU1        ----                    ----   lock(pcp_batch_high_lock);                                lock(cpu_hotplug_lock);                                lock(pcp_batch_high_lock);   rlock(cpu_hotplug_lock);   *** DEADLOCK ***  5 locks held by bash/46904:  #0: ffff98f6c3bb23f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0  #1: ffff98f6c328e488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0  #2: ffff98ef83b31890 (kn->active#113){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0  #3: ffffffffabf9db48 (mf_mutex){+.+.}-{3:3}, at: memory_failure+0x44/0xc70  #4: ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40  stack backtrace: CPU: 10 PID: 46904 Comm: bash Kdump: loaded Not tainted 6.8.0-11409-gf6cef5f8c37f #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace:  <TASK>  dump_stack_lvl+0x68/0xa0  check_noncircular+0x129/0x140  __lock_acquire+0x1298/0x1cd0  lock_acquire+0xc0/0x2b0  cpus_read_lock+0x2a/0xc0  static_key_slow_dec+0x16/0x60  __hugetlb_vmemmap_restore_folio+0x1b9/0x200  dissolve_free_huge_page+0x211/0x260  __page_handle_poison+0x45/0xc0  memory_failure+0x65e/0xc70  hard_offline_page_store+0x55/0xa0  kernfs_fop_write_iter+0x12c/0x1d0  vfs_write+0x387/0x550  ksys_write+0x64/0xe0  do_syscall_64+0xca/0x1e0  entry_SYSCALL_64_after_hwframe+0x6d/0x75 RIP: 0033:0x7fc862314887 Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 RSP: 002b:00007fff19311268 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007fc862314887 RDX: 000000000000000c RSI: 000056405645fe10 RDI: 0000000000000001 RBP: 000056405645fe10 R08: 00007fc8623d1460 R09: 000000007fffffff R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c R13: 00007fc86241b780 R14: 00007fc862417600 R15: 00007fc862416a00  In short, below scene breaks the  ---truncated---