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:

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 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---