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SubjectBUG: double free of mlx5_cmd_work_ent during shutdown
Hi,

When force teardown is used (for devices that doesn't support fast
teardown), mlx5_cmd_force_teardown_hca() sends out a TEARDOWN_HCA command,
wait for the command to complete, and call cmd_ent_put() from the
following stack.

cmd_exec() {
// ...
out_free:
cmd_ent_put(ent); // HERE
out:
return err;
}
mlx5_cmd_exec_polling()
mlx5_cmd_force_teardown_hca()
shutdown()

However, there's another path which cmd_ent_put() is called for the same
command from the async events chain.

mlx5_cmd_comp_handler() {
for (i = 0; i < (1 << cmd->log_sz); i++) {
if (test_bit(i, &vector)) {
// ...
if (!forced || /* Real FW completion */
pci_channel_offline(dev->pdev) || /* FW is inaccessible */
dev->state == MLX5_DEVICE_STATE_INTERNAL_ERROR)
cmd_ent_put(ent); // HERE
// ...
}
cmd_comp_notifier()
notifier_call_chain()
atomic_notifier_call_chain()
mlx5_eq_async_int()
notifier_call_chain()
atomic_notifier_call_chain()
mlx5_irq_int_handler()

This leads to to "refcount_t: underflow; use-after-free" warning during
shutdown.

---

Here's the stack trace on v5.13-based kernel with KASAN enabled.
(Line number doesn't exactly match though)

systemd-shutdown[1]: Rebooting with kexec.
kvm: exiting hardware virtualization
sd 0:0:0:0: [sda] Synchronizing SCSI cache
mlx5_core 0000:0a:00.1: Shutdown was called
mlx5_try_fast_unload:1629: mlx5_core 0000:0a:00.1: mlx5_try_fast_unload:1629:(pid 4959): force teardown firmware support=1
mlx5_try_fast_unload:1630: mlx5_core 0000:0a:00.1: mlx5_try_fast_unload:1630:(pid 4959): fast teardown firmware support=0
mlx5_cmd_fast_teardown_hca:330: mlx5_core 0000:0a:00.1: mlx5_cmd_fast_teardown_hca:330:(pid 4959): fast teardown is not supported in the firmware
dump_command:805: mlx5_core 0000:0a:00.1: dump_command:805:(pid 4647): cmd[0]: start dump
dump_command:814: mlx5_core 0000:0a:00.1: dump_command:814:(pid 4647): cmd[0]: dump command TEARDOWN_HCA(0x103) INPUT
dump_buf:272: cmd[0]: 000: 07000000 00000010 00000000 00000000
dump_buf:272: cmd[0]: 010: 01030000 00000000 00000001 00000000
dump_buf:272: cmd[0]: 020: 00000000 00000000 00000000 00000000
dump_buf:272: cmd[0]: 030: 00000000 00000000 00000010 3fc50001
dump_buf:279:
dump_command:848: mlx5_core 0000:0a:00.1: dump_command:848:(pid 4647): cmd[0]: end dump
cmd_work_handler:1003: mlx5_core 0000:0a:00.1: cmd_work_handler:1003:(pid 4647): writing 0x1 to command doorbell
dump_command:805: mlx5_core 0000:0a:00.1: dump_command:805:(pid 4647): cmd[0]: start dump
mlx5_core 0000:0a:00.1: mlx5_cmd_comp_handler:1613:(pid 0): Command completion arrived after timeout (entry idx = 0).
dump_command:814: mlx5_core 0000:0a:00.1: dump_command:814:(pid 4647): cmd[0]: dump command TEARDOWN_HCA(0x103) OUTPUT

cmd_ent_put(00000000fbaea4c6) will be called in mlx5_cmd_comp_handler:1615 for TEARDOWN_HCA(0x103), polling 1, ret 0
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

any_notifier:148: mlx5_core 0000:0a:00.1: any_notifier:148:(pid 0): Async eqe type MLX5_EVENT_TYPE_CMD, subtype (0)
==================================================================
BUG: KASAN: use-after-free in dump_command+0x9d9/0xa40 [mlx5_core]
Read of size 4 at addr ffff8881120620e0 by task kworker/u96:0/4647

CPU: 10 PID: 4647 Comm: kworker/u96:0 Tainted: G E 5.14.0-rc1-1-default+ #7 6ab45f24446e456129f9451daed46c2a2aa80406
Hardware name: Dell Inc. PowerEdge T320/0FDT3J, BIOS 2.9.0 01/08/2020
Workqueue: mlx5_cmd_0000:0a:00.1 cmd_work_handler [mlx5_core]
Call Trace:
dump_stack_lvl+0x57/0x72
print_address_description.constprop.0+0x1f/0x140
? dump_command+0x9d9/0xa40 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
kasan_report.cold+0x7f/0x11b
? dump_command+0x9d9/0xa40 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
dump_command+0x9d9/0xa40 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? seqcount_lockdep_reader_access.constprop.0+0x84/0x90
? seqcount_lockdep_reader_access.constprop.0+0x84/0x90
mlx5_cmd_comp_handler+0x498/0x13e0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? lock_release+0x1ea/0x6c0
? mlx5_cmd_check+0x2f0/0x2f0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? lockdep_hardirqs_on_prepare+0x278/0x3e0
? seqcount_lockdep_reader_access.constprop.0+0x84/0x90
? cmd_work_handler+0xfa2/0x19a0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? __cond_resched+0x15/0x30
cmd_work_handler+0xfa2/0x19a0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? cmd_comp_notifier+0x90/0x90 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? lock_is_held_type+0xe0/0x110
? lockdep_hardirqs_on_prepare+0x278/0x3e0
process_one_work+0x8b2/0x14c0
? lock_release+0x6c0/0x6c0
? pwq_dec_nr_in_flight+0x260/0x260
? rwlock_bug.part.0+0x90/0x90
worker_thread+0x544/0x12d0
? get_cpu_entry_area+0x13/0x20
? __kthread_parkme+0xa5/0x130
? process_one_work+0x14c0/0x14c0
kthread+0x349/0x410
? _raw_spin_unlock_irq+0x24/0x40
? set_kthread_struct+0x100/0x100
ret_from_fork+0x22/0x30

Allocated by task 4959:
kasan_save_stack+0x1b/0x40
__kasan_kmalloc+0x7c/0x90
cmd_exec+0x6f0/0x1740 [mlx5_core]
mlx5_cmd_exec_polling+0x1f/0x40 [mlx5_core]
mlx5_cmd_force_teardown_hca+0xfc/0x200 [mlx5_core]
shutdown+0x2e7/0x3b3 [mlx5_core]
pci_device_shutdown+0x75/0x110
device_shutdown+0x2ce/0x5e0
kernel_kexec+0x57/0xb0
__do_sys_reboot+0x284/0x2f0
do_syscall_64+0x5c/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 0:
kasan_save_stack+0x1b/0x40
kasan_set_track+0x1c/0x30
kasan_set_free_info+0x20/0x30
__kasan_slab_free+0xec/0x120
slab_free_freelist_hook+0x90/0x1b0
kfree+0xd1/0x410
mlx5_cmd_comp_handler.cold+0x138/0x16c [mlx5_core]
cmd_comp_notifier+0x72/0x90 [mlx5_core]
atomic_notifier_call_chain+0xdd/0x1c0
mlx5_eq_async_int+0x34c/0x8f0 [mlx5_core]
atomic_notifier_call_chain+0xdd/0x1c0
irq_int_handler+0x11/0x20 [mlx5_core]
__handle_irq_event_percpu+0x264/0x640
handle_irq_event+0x10b/0x270
handle_edge_irq+0x21a/0xbe0
__common_interrupt+0x72/0x160
common_interrupt+0x7b/0xa0
asm_common_interrupt+0x1e/0x40

Last potentially related work creation:
kasan_save_stack+0x1b/0x40
kasan_record_aux_stack+0xa5/0xb0
insert_work+0x44/0x280
__queue_work+0x4b7/0xc50
queue_work_on+0x8d/0x90
cmd_exec+0xfac/0x1740 [mlx5_core]
mlx5_cmd_exec_polling+0x1f/0x40 [mlx5_core]
mlx5_cmd_force_teardown_hca+0xfc/0x200 [mlx5_core]
shutdown+0x2e7/0x3b3 [mlx5_core]
pci_device_shutdown+0x75/0x110
device_shutdown+0x2ce/0x5e0
kernel_kexec+0x57/0xb0
__do_sys_reboot+0x284/0x2f0
do_syscall_64+0x5c/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff888112062000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 224 bytes inside of
1024-byte region [ffff888112062000, ffff888112062400)
The buggy address belongs to the page:
page:000000008b314a5c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112060
head:000000008b314a5c order:3 compound_mapcount:0 compound_pincount:0
flags: 0x2ffff800010200(slab|head|node=0|zone=2|lastcpupid=0x1ffff)
raw: 002ffff800010200 ffffea00041e3a00 0000000500000005 ffff888100042dc0
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888112061f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888112062000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888112062080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888112062100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888112062180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Disabling lock debugging due to kernel taint
dump_buf:272: cmd[0]: 000: 07000000 00000010 00000000 00000000
dump_buf:272: cmd[0]: 010: 01030000 00000000 00000001 00000000
dump_buf:272: cmd[0]: 020: 00000000 00000000 00000000 00000001
dump_buf:272: cmd[0]: 030: 00000000 00000000 00000010 3fc50000
dump_buf:279:
dump_command:848: mlx5_core 0000:0a:00.1: dump_command:848:(pid 4647): cmd[0]: end dump
mlx5_cmd_comp_handler:1648: mlx5_core 0000:0a:00.1: mlx5_cmd_comp_handler:1648:(pid 4647): command completed. ret 0x0, delivery status no errors(0x0)
wait_func:1102: mlx5_core 0000:0a:00.1: wait_func:1102:(pid 4959): err 0, delivery status no errors(0)

cmd_ent_put(00000000fbaea4c6) will be called in mlx5_cmd_invoke:1178 for TEARDOWN_HCA(0x103), polling 1, ret 0
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 2 PID: 4959 at lib/refcount.c:28 refcount_warn_saturate+0xaa/0x140
Modules linked in: af_packet(E) bridge(E) stp(E) llc(E) iscsi_ibft(E) iscsi_boot_sysfs(E) rfkill(E) mlx5_core(E) intel_rapl_msr(E) intel_rapl_common(E) sb_edac(E) x86_pkg_temp_thermal(E) intel_powerclamp(E) mgag200(E) coretemp(E) kvm_intel(E) drm_kms_helper(E) kvm(E) syscopyarea(E) sysfillrect(E) ipmi_ssif(E) sysimgblt(E) joydev(E) fb_sys_fops(E) dcdbas(E) cec(E) tg3(E) nls_iso8859_1(E) iTCO_wdt(E) nls_cp437(E) irqbypass(E) rc_core(E) libphy(E) intel_pmc_bxt(E) mei_me(E) ipmi_si(E) vfat(E) i2c_algo_bit(E) mlxfw(E) efi_pstore(E) fat(E) ipmi_devintf(E) iTCO_vendor_support(E) pcspkr(E) pci_hyperv_intf(E) ipmi_msghandler(E) psample(E) tiny_power_button(E) mei(E) lpc_ich(E) wmi(E) button(E) drm(E) fuse(E) configfs(E) hid_microsoft(E) ff_memless(E) hid_generic(E) usbhid(E) crct10dif_pclmul(E) crc32_pclmul(E) crc32c_intel(E) ghash_clmulni_intel(E) aesni_intel(E) crypto_simd(E) cryptd(E) ehci_pci(E) ehci_hcd(E) usbcore(E) sg(E) efivarfs(E)
CPU: 2 PID: 4959 Comm: kexec Tainted: G B E 5.14.0-rc1-1-default+ #7 6ab45f24446e456129f9451daed46c2a2aa80406
Hardware name: Dell Inc. PowerEdge T320/0FDT3J, BIOS 2.9.0 01/08/2020
RIP: 0010:refcount_warn_saturate+0xaa/0x140
Code: e9 0c b5 02 01 e8 be 45 f9 00 0f 0b eb d5 80 3d d7 0c b5 02 00 75 cc 48 c7 c7 e0 f0 a4 ad c6 05 c7 0c b5 02 01 e8 9e 45 f9 00 <0f> 0b eb b5 80 3d b5 0c b5 02 00 75 ac 48 c7 c7 a0 f1 a4 ad c6 05
RSP: 0018:ffff8881593b79d8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff888112062214 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffed102b276f2d
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffed102b276eca R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888159585908 R15: ffff8881079fa080
FS: 00007f8846e63740(0000) GS:ffff8881d3700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f884700b670 CR3: 0000000112ef0004 CR4: 00000000001706e0
Call Trace:
cmd_exec+0xda6/0x1740 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? cb_timeout_handler+0xa0/0xa0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? mark_held_locks+0x9e/0xe0
mlx5_cmd_exec_polling+0x1f/0x40 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
mlx5_cmd_force_teardown_hca+0xfc/0x200 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
? mlx5_cmd_teardown_hca+0xd0/0xd0 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
shutdown+0x2e7/0x3b3 [mlx5_core 159b773d3cc25877247f038573d06bc052f8250f]
pci_device_shutdown+0x75/0x110
device_shutdown+0x2ce/0x5e0
kernel_kexec+0x57/0xb0
__do_sys_reboot+0x284/0x2f0
? poweroff_work_func+0x90/0x90
? lockdep_hardirqs_on_prepare+0x278/0x3e0
? kasan_quarantine_put+0x8e/0x1e0
? lockdep_hardirqs_on+0x77/0xf0
? kasan_quarantine_put+0x8e/0x1e0
? lock_is_held_type+0xe0/0x110
? slab_free_freelist_hook+0x90/0x1b0
? __fput+0x2a1/0x780
? lock_is_held_type+0x53/0x110
? rcu_read_lock_sched_held+0x3f/0x80
? lockdep_hardirqs_on_prepare+0x278/0x3e0
? call_rcu+0x5b2/0xa80
? lock_is_held_type+0x53/0x110
? lockdep_hardirqs_on_prepare+0x278/0x3e0
? syscall_enter_from_user_mode+0x21/0x70
do_syscall_64+0x5c/0xc0
? lockdep_hardirqs_on_prepare+0x278/0x3e0
? lockdep_hardirqs_on+0x77/0xf0
? do_syscall_64+0x69/0xc0
? do_syscall_64+0x69/0xc0
? lock_is_held_type+0x53/0x110
? irqentry_exit_to_user_mode+0xa/0x40
? asm_exc_page_fault+0x8/0x30
? lockdep_hardirqs_on+0x77/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f8846faa0d7
Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 89 fa be 69 19 12 28 bf ad de e1 fe b8 a9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 69 ad 0c 00 f7 d8 64 89 02 b8
RSP: 002b:00007fffeb69d648 EFLAGS: 00000206 ORIG_RAX: 00000000000000a9
RAX: ffffffffffffffda RBX: 0000561e00f46520 RCX: 00007f8846faa0d7
RDX: 0000000045584543 RSI: 0000000028121969 RDI: 00000000fee1dead
RBP: 00007f8847076600 R08: 000000000000000b R09: 0000000000000000
R10: 00007f8846ebe0d8 R11: 0000000000000206 R12: 0000561dffc738fe
R13: 0000561dffc73905 R14: 00007fffeb69d7a0 R15: 00000000ffffffff
irq event stamp: 11228
hardirqs last enabled at (11227): [<ffffffffad2dde14>] _raw_spin_unlock_irq+0x24/0x40
hardirqs last disabled at (11228): [<ffffffffad2c9f39>] __schedule+0x1229/0x2300
softirqs last enabled at (11162): [<ffffffffab3bd94e>] __irq_exit_rcu+0x12e/0x170
softirqs last disabled at (11157): [<ffffffffab3bd94e>] __irq_exit_rcu+0x12e/0x170
---[ end trace 151c2ed42dd09eaf ]---
cmd_exec:1864: mlx5_core 0000:0a:00.1: cmd_exec:1864:(pid 4959): err 0, status 0
mlx5_core 0000:0a:00.1: mlx5_cmd_force_teardown_hca:313:(pid 4959): teardown with force mode failed, doing normal teardown
mlx5_try_fast_unload:1654: mlx5_core 0000:0a:00.1: mlx5_try_fast_unload:1654:(pid 4959): Firmware couldn't do fast unload error: -5
mlx5_wait_for_pages:739: mlx5_core 0000:0a:00.1: mlx5_wait_for_pages:739:(pid 4959): Waiting for 0 pages
mlx5_wait_for_pages:752: mlx5_core 0000:0a:00.1: mlx5_wait_for_pages:752:(pid 4959): All pages received
dump_command:805: mlx5_core 0000:0a:00.1: dump_command:805:(pid 4647): cmd[0]: start dump
dump_command:814: mlx5_core 0000:0a:00.1: dump_command:814:(pid 4647): cmd[0]: dump command DESTROY_FLOW_TABLE(0x931) INPUT
dump_buf:272: cmd[0]: 000: 07000000 00000040 00000001 347e4400
dump_buf:272: cmd[0]: 010: 09310000 00000000 00000000 00000000
dump_buf:272: cmd[0]: 020: 00000000 00000000 00000000 00000000
dump_buf:272: cmd[0]: 030: 00000000 00000000 00000010 40de0001


Best,
Shung-Hsi Yu

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