Hi,
sorry for the late response.
From: Steve French <smfrench@xxxxxxxxx>
Date: Tue, 17 Dec 2024 21:24:12 -0600
> Enzo had an interesting patch, that seems to fix an important problem.
>
> Here was his repro scenario:
>
> tw:~ # mount.cifs -o credentials=/root/wincreds,echo_interval=10
> //someserver/target1 /mnt/test
> tw:~ # ls /mnt/test
> abc dir1 dir3 target1_file.txt tsub
> tw:~ # iptables -A INPUT -s someserver -j DROP
>
> Trigger reconnect and wait for 3*echo_interval:
>
> tw:~ # cat /mnt/test/target1_file.txt
> cat: /mnt/test/target1_file.txt: Host is down
>
> Then umount and rmmod. Note that rmmod might take several iterations
> until it properly tears down everything, so make sure you see the "not
> loaded" message before proceeding:
>
> tw:~ # umount /mnt/*; rmmod cifs
> umount: /mnt/az: not mounted.
> umount: /mnt/dfs: not mounted.
> umount: /mnt/local: not mounted.
> umount: /mnt/scratch: not mounted.
> rmmod: ERROR: Module cifs is in use
> ...
> tw:~ # rmmod cifs
> rmmod: ERROR: Module cifs is not currently loaded
>
> Then kickoff the TCP internals:
> tw:~ # iptables -F
>
> Gets the lockdep warning (requires CONFIG_LOCKDEP=y) + a NULL deref
> later on.
I tried the repro and confirmed it triggers null deref.
It happens in LOCKDEP internal, so for me it looks like a problem in
LOCKDEP rather than CIFS or TCP.
I think LOCKDEP should hold a module reference and prevent related
modules from being unloaded.
[ 242.144225][ C0] ------------[ cut here ]------------
[ 242.144562][ C0] DEBUG_LOCKS_WARN_ON(1)
[ 242.144575][ C0] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:232 hlock_class+0xf9/0x130
[ 242.145435][ C0] Modules linked in: [last unloaded: cifs]
[ 242.145820][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.12.0-rc4-01014-g835f27aa21c9 #25
[ 242.146426][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 242.147197][ C0] RIP: 0010:hlock_class+0xf9/0x130
[ 242.147529][ C0] Code: b6 14 11 38 d0 7c 04 84 d2 75 47 8b 05 54 a5 6b 04 85 c0 75 19 90 48 c7 c6 e0 e1 46 84 48 c7 c7 c0 dd 46 84 e8 88 6d eb ff 90 <0f> 0b 90 90 90 31 c0 5b c3 cc cc cc cc e8 05 91 4d 00 e9 19 ff ff
[ 242.148779][ C0] RSP: 0018:ff1100006c009138 EFLAGS: 00010082
[ 242.149168][ C0] RAX: 0000000000000000 RBX: 00000000000004e4 RCX: 0000000000000027
[ 242.149673][ C0] RDX: 0000000000000027 RSI: 0000000000000004 RDI: ff1100006c1e8a08
[ 242.150180][ C0] RBP: 0000000000000000 R08: 0000000000000001 R09: ffe21c000d83d141
[ 242.150688][ C0] R10: ff1100006c1e8a0b R11: 0000000000000017 R12: 0000000000000000
[ 242.151199][ C0] R13: ffffffff8502e6c0 R14: ffffffff8502f150 R15: 00000000000424e4
[ 242.151706][ C0] FS: 0000000000000000(0000) GS:ff1100006c000000(0000) knlGS:0000000000000000
[ 242.152275][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 242.152693][ C0] CR2: 00007ffd0d2666b8 CR3: 0000000010002002 CR4: 0000000000771ef0
[ 242.153197][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 242.153698][ C0] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[ 242.154200][ C0] PKRU: 55555554
[ 242.154426][ C0] Call Trace:
[ 242.154636][ C0] <IRQ>
[ 242.154817][ C0] ? __warn+0xcc/0x2e0
[ 242.155086][ C0] ? hlock_class+0xf9/0x130
[ 242.155378][ C0] ? report_bug+0x28c/0x2d0
[ 242.155678][ C0] ? handle_bug+0x54/0xa0
[ 242.155954][ C0] ? exc_invalid_op+0x18/0x50
[ 242.156250][ C0] ? asm_exc_invalid_op+0x1a/0x20
[ 242.156579][ C0] ? hlock_class+0xf9/0x130
[ 242.156867][ C0] ? hlock_class+0xf8/0x130
[ 242.157154][ C0] __lock_acquire+0x4d8/0x3c30
[ 242.157459][ C0] ? find_held_lock+0x33/0x120
[ 242.157766][ C0] ? __pfx___lock_acquire+0x10/0x10
[ 242.158095][ C0] ? __pfx_lock_release+0x10/0x10
[ 242.158414][ C0] lock_acquire+0x196/0x520
[ 242.158699][ C0] ? tcp_v4_rcv+0x2695/0x3b70
[ 242.158999][ C0] ? __pfx_lock_acquire+0x10/0x10
[ 242.159325][ C0] ? __pfx_tcp_inbound_hash+0x10/0x10
[ 242.159673][ C0] ? __pfx_sk_filter_trim_cap+0x10/0x10
[ 242.160039][ C0] ? kasan_quarantine_put+0x84/0x1d0
[ 242.160382][ C0] _raw_spin_lock_nested+0x2e/0x70
[ 242.160707][ C0] ? tcp_v4_rcv+0x2695/0x3b70
[ 242.161004][ C0] tcp_v4_rcv+0x2695/0x3b70
[ 242.161292][ C0] ? __pfx_tcp_v4_rcv+0x10/0x10
[ 242.161598][ C0] ? ip_local_deliver_finish+0x204/0x490
[ 242.161960][ C0] ? __pfx_raw_local_deliver+0x10/0x10
[ 242.162308][ C0] ? hlock_class+0x4e/0x130
[ 242.162598][ C0] ? lock_release+0x5d5/0xb00
[ 242.162898][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.163223][ C0] ip_protocol_deliver_rcu+0x8e/0x330
[ 242.163568][ C0] ip_local_deliver_finish+0x2bd/0x490
[ 242.163922][ C0] ip_local_deliver+0x198/0x450
[ 242.164236][ C0] ? __pfx_ip_local_deliver+0x10/0x10
[ 242.164579][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.164896][ C0] ? __pfx_ip_local_deliver_finish+0x10/0x10
[ 242.165273][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.165594][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.165921][ C0] ip_sublist_rcv_finish+0x1e7/0x410
[ 242.166260][ C0] ip_sublist_rcv+0x380/0x760
[ 242.166564][ C0] ? __pfx_ip_sublist_rcv+0x10/0x10
[ 242.166898][ C0] ? hlock_class+0x4e/0x130
[ 242.167187][ C0] ? __lock_acquire+0x15e6/0x3c30
[ 242.167506][ C0] ? ip_fast_csum+0xc/0x20
[ 242.167789][ C0] ? ip_rcv_core+0x5dd/0xd30
[ 242.168084][ C0] ip_list_rcv+0x26e/0x380
[ 242.168367][ C0] ? __pfx_ip_list_rcv+0x10/0x10
[ 242.168684][ C0] __netif_receive_skb_list_core+0x5c2/0x830
[ 242.169063][ C0] ? __pfx___netif_receive_skb_list_core+0x10/0x10
[ 242.169470][ C0] ? lockdep_hardirqs_on_prepare+0x12b/0x3f0
[ 242.169844][ C0] ? kvm_clock_get_cycles+0x18/0x30
[ 242.170174][ C0] ? ktime_get_with_offset+0xe3/0x240
[ 242.170520][ C0] netif_receive_skb_list_internal+0x595/0xc70
[ 242.170905][ C0] ? __pfx_netif_receive_skb_list_internal+0x10/0x10
[ 242.171321][ C0] ? __kasan_mempool_unpoison_object+0x11e/0x1e0
[ 242.171721][ C0] ? napi_gro_receive+0x792/0x9d0
[ 242.172040][ C0] napi_complete_done+0x19d/0x700
[ 242.172359][ C0] ? __pfx_napi_complete_done+0x10/0x10
[ 242.172709][ C0] ? __pfx_e1000_clean_rx_irq+0x10/0x10
[ 242.173061][ C0] e1000_clean+0x85f/0x23e0
[ 242.173347][ C0] ? hlock_class+0x4e/0x130
[ 242.173636][ C0] ? __pfx_e1000_clean+0x10/0x10
[ 242.173953][ C0] __napi_poll.constprop.0+0x9b/0x430
[ 242.174296][ C0] net_rx_action+0x8d4/0xc90
[ 242.174594][ C0] ? __pfx_net_rx_action+0x10/0x10
[ 242.174919][ C0] ? handle_irq_event+0x10d/0x1c0
[ 242.175246][ C0] ? find_held_lock+0x33/0x120
[ 242.175556][ C0] ? hlock_class+0x4e/0x130
[ 242.175855][ C0] ? lock_release+0x5d5/0xb00
[ 242.176157][ C0] ? __pfx_lock_release+0x10/0x10
[ 242.176478][ C0] ? kvm_guest_apic_eoi_write+0x1e/0x40
[ 242.176831][ C0] handle_softirqs+0x1ae/0x770
[ 242.177137][ C0] irq_exit_rcu+0x94/0xc0
[ 242.177413][ C0] common_interrupt+0x7e/0x90
[ 242.177716][ C0] </IRQ>
[ 242.177904][ C0] <TASK>
[ 242.178093][ C0] asm_common_interrupt+0x26/0x40
[ 242.178415][ C0] RIP: 0010:default_idle+0xf/0x20
[ 242.178738][ C0] Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 13 df 32 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
[ 242.179958][ C0] RSP: 0018:ffffffff85007e30 EFLAGS: 00000206
[ 242.180341][ C0] RAX: 000000000007b609 RBX: 0000000000000000 RCX: ffffffff840f7d25
[ 242.180849][ C0] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8125f83d
[ 242.181357][ C0] RBP: dffffc0000000000 R08: 0000000000000001 R09: ffe21c000d83ecb8
[ 242.181864][ C0] R10: ff1100006c1f65c3 R11: 0000000000000000 R12: ffffffff8595b388
[ 242.182371][ C0] R13: 1ffffffff0a00fcb R14: 0000000000000000 R15: 0000000000000000
[ 242.182877][ C0] ? ct_kernel_exit.constprop.0+0xc5/0xf0
[ 242.183240][ C0] ? do_idle+0x2fd/0x3b0
[ 242.183508][ C0] default_idle_call+0x6d/0xb0
[ 242.183811][ C0] do_idle+0x2fd/0x3b0
[ 242.184072][ C0] ? __pfx_do_idle+0x10/0x10
[ 242.184368][ C0] cpu_startup_entry+0x4f/0x60
[ 242.184673][ C0] rest_init+0x139/0x200
[ 242.184945][ C0] ? acpi_subsystem_init+0x50/0x140
[ 242.185280][ C0] start_kernel+0x374/0x3f0
[ 242.185573][ C0] x86_64_start_reservations+0x18/0x30
[ 242.185925][ C0] x86_64_start_kernel+0xcf/0xe0
[ 242.186236][ C0] common_startup_64+0x12c/0x138
[ 242.186551][ C0] </TASK>
[ 242.186740][ C0] irq event stamp: 505362
[ 242.187010][ C0] hardirqs last enabled at (505362): [<ffffffff81171ea1>] __local_bh_enable_ip+0xa1/0x110
[ 242.187632][ C0] hardirqs last disabled at (505361): [<ffffffff81171eca>] __local_bh_enable_ip+0xca/0x110
[ 242.188252][ C0] softirqs last enabled at (505348): [<ffffffff81171a8c>] handle_softirqs+0x50c/0x770
[ 242.188851][ C0] softirqs last disabled at (505355): [<ffffffff81172174>] irq_exit_rcu+0x94/0xc0
[ 242.189424][ C0] ---[ end trace 0000000000000000 ]---
[ 242.189778][ C0] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000018: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 242.190575][ C0] KASAN: null-ptr-deref in range [0x00000000000000c0-0x00000000000000c7]
[ 242.191097][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G W 6.12.0-rc4-01014-g835f27aa21c9 #25
[ 242.191782][ C0] Tainted: [W]=WARN
[ 242.192023][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 242.192788][ C0] RIP: 0010:__lock_acquire+0x4f0/0x3c30
[ 242.193137][ C0] Code: 84 24 40 01 00 00 4c 89 f7 41 89 46 34 e8 e8 27 ff ff 48 ba 00 00 00 00 00 fc ff df 48 8d b8 c4 00 00 00 48 89 f9 48 c1 e9 03 <0f> b6 14 11 48 89 f9 83 e1 07 38 ca 7f 08 84 d2 0f 85 b6 29 00 00
[ 242.194860][ C0] RSP: 0018:ff1100006c009148 EFLAGS: 00010007
[ 242.195251][ C0] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000018
[ 242.195758][ C0] RDX: dffffc0000000000 RSI: 0000000000000004 RDI: 00000000000000c4
[ 242.196253][ C0] RBP: 0000000000000000 R08: 0000000000000001 R09: ffe21c000d83d141
[ 242.196750][ C0] R10: ff1100006c1e8a0b R11: 0000000000000017 R12: 0000000000000000
[ 242.197245][ C0] R13: ffffffff8502e6c0 R14: ffffffff8502f150 R15: 00000000000424e4
[ 242.197742][ C0] FS: 0000000000000000(0000) GS:ff1100006c000000(0000) knlGS:0000000000000000
[ 242.198301][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 242.198715][ C0] CR2: 00007ffd0d2666b8 CR3: 0000000010002002 CR4: 0000000000771ef0
[ 242.199212][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 242.199703][ C0] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[ 242.200200][ C0] PKRU: 55555554
[ 242.200424][ C0] Call Trace:
[ 242.200635][ C0] <IRQ>
[ 242.200816][ C0] ? die_addr+0x3c/0xa0
[ 242.201084][ C0] ? exc_general_protection+0x14d/0x230
[ 242.201433][ C0] ? asm_exc_general_protection+0x26/0x30
[ 242.201793][ C0] ? __lock_acquire+0x4f0/0x3c30
[ 242.202103][ C0] ? __lock_acquire+0x4d8/0x3c30
[ 242.202414][ C0] ? find_held_lock+0x33/0x120
[ 242.202715][ C0] ? __pfx___lock_acquire+0x10/0x10
[ 242.203040][ C0] ? __pfx_lock_release+0x10/0x10
[ 242.203355][ C0] lock_acquire+0x196/0x520
[ 242.203639][ C0] ? tcp_v4_rcv+0x2695/0x3b70
[ 242.203934][ C0] ? __pfx_lock_acquire+0x10/0x10
[ 242.204246][ C0] ? __pfx_tcp_inbound_hash+0x10/0x10
[ 242.204577][ C0] ? __pfx_sk_filter_trim_cap+0x10/0x10
[ 242.204923][ C0] ? kasan_quarantine_put+0x84/0x1d0
[ 242.205257][ C0] _raw_spin_lock_nested+0x2e/0x70
[ 242.205586][ C0] ? tcp_v4_rcv+0x2695/0x3b70
[ 242.205883][ C0] tcp_v4_rcv+0x2695/0x3b70
[ 242.206170][ C0] ? __pfx_tcp_v4_rcv+0x10/0x10
[ 242.206475][ C0] ? ip_local_deliver_finish+0x204/0x490
[ 242.206828][ C0] ? __pfx_raw_local_deliver+0x10/0x10
[ 242.207166][ C0] ? hlock_class+0x4e/0x130
[ 242.207446][ C0] ? lock_release+0x5d5/0xb00
[ 242.207736][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.208047][ C0] ip_protocol_deliver_rcu+0x8e/0x330
[ 242.208380][ C0] ip_local_deliver_finish+0x2bd/0x490
[ 242.208719][ C0] ip_local_deliver+0x198/0x450
[ 242.209021][ C0] ? __pfx_ip_local_deliver+0x10/0x10
[ 242.209351][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.209661][ C0] ? __pfx_ip_local_deliver_finish+0x10/0x10
[ 242.210030][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.210342][ C0] ? lock_is_held_type+0xa0/0x120
[ 242.210655][ C0] ip_sublist_rcv_finish+0x1e7/0x410
[ 242.210982][ C0] ip_sublist_rcv+0x380/0x760
[ 242.211274][ C0] ? __pfx_ip_sublist_rcv+0x10/0x10
[ 242.211594][ C0] ? hlock_class+0x4e/0x130
[ 242.211873][ C0] ? __lock_acquire+0x15e6/0x3c30
[ 242.212186][ C0] ? ip_fast_csum+0xc/0x20
[ 242.212460][ C0] ? ip_rcv_core+0x5dd/0xd30
[ 242.212746][ C0] ip_list_rcv+0x26e/0x380
[ 242.213021][ C0] ? __pfx_ip_list_rcv+0x10/0x10
[ 242.213328][ C0] __netif_receive_skb_list_core+0x5c2/0x830
[ 242.213699][ C0] ? __pfx___netif_receive_skb_list_core+0x10/0x10
[ 242.214103][ C0] ? lockdep_hardirqs_on_prepare+0x12b/0x3f0
[ 242.214477][ C0] ? kvm_clock_get_cycles+0x18/0x30
[ 242.214807][ C0] ? ktime_get_with_offset+0xe3/0x240
[ 242.215139][ C0] netif_receive_skb_list_internal+0x595/0xc70
[ 242.215520][ C0] ? __pfx_netif_receive_skb_list_internal+0x10/0x10
[ 242.215934][ C0] ? __kasan_mempool_unpoison_object+0x11e/0x1e0
[ 242.216324][ C0] ? napi_gro_receive+0x792/0x9d0
[ 242.216633][ C0] napi_complete_done+0x19d/0x700
[ 242.216941][ C0] ? __pfx_napi_complete_done+0x10/0x10
[ 242.217280][ C0] ? __pfx_e1000_clean_rx_irq+0x10/0x10
[ 242.217618][ C0] e1000_clean+0x85f/0x23e0
[ 242.217897][ C0] ? hlock_class+0x4e/0x130
[ 242.218173][ C0] ? __pfx_e1000_clean+0x10/0x10
[ 242.218477][ C0] __napi_poll.constprop.0+0x9b/0x430
[ 242.218807][ C0] net_rx_action+0x8d4/0xc90
[ 242.219092][ C0] ? __pfx_net_rx_action+0x10/0x10
[ 242.219406][ C0] ? handle_irq_event+0x10d/0x1c0
[ 242.219719][ C0] ? find_held_lock+0x33/0x120
[ 242.220014][ C0] ? hlock_class+0x4e/0x130
[ 242.220293][ C0] ? lock_release+0x5d5/0xb00
[ 242.220581][ C0] ? __pfx_lock_release+0x10/0x10
[ 242.220887][ C0] ? kvm_guest_apic_eoi_write+0x1e/0x40
[ 242.221227][ C0] handle_softirqs+0x1ae/0x770
[ 242.221527][ C0] irq_exit_rcu+0x94/0xc0
[ 242.221793][ C0] common_interrupt+0x7e/0x90
[ 242.222081][ C0] </IRQ>
[ 242.222262][ C0] <TASK>
[ 242.222443][ C0] asm_common_interrupt+0x26/0x40
[ 242.222754][ C0] RIP: 0010:default_idle+0xf/0x20
[ 242.223063][ C0] Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 13 df 32 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
[ 242.224245][ C0] RSP: 0018:ffffffff85007e30 EFLAGS: 00000206
[ 242.224619][ C0] RAX: 000000000007b609 RBX: 0000000000000000 RCX: ffffffff840f7d25
[ 242.225113][ C0] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8125f83d
[ 242.225596][ C0] RBP: dffffc0000000000 R08: 0000000000000001 R09: ffe21c000d83ecb8
[ 242.226077][ C0] R10: ff1100006c1f65c3 R11: 0000000000000000 R12: ffffffff8595b388
[ 242.226560][ C0] R13: 1ffffffff0a00fcb R14: 0000000000000000 R15: 0000000000000000
[ 242.227044][ C0] ? ct_kernel_exit.constprop.0+0xc5/0xf0
[ 242.227393][ C0] ? do_idle+0x2fd/0x3b0
[ 242.227655][ C0] default_idle_call+0x6d/0xb0
[ 242.227948][ C0] do_idle+0x2fd/0x3b0
[ 242.228201][ C0] ? __pfx_do_idle+0x10/0x10
[ 242.228486][ C0] cpu_startup_entry+0x4f/0x60
[ 242.228781][ C0] rest_init+0x139/0x200
[ 242.229043][ C0] ? acpi_subsystem_init+0x50/0x140
[ 242.229361][ C0] start_kernel+0x374/0x3f0
[ 242.229637][ C0] x86_64_start_reservations+0x18/0x30
[ 242.229969][ C0] x86_64_start_kernel+0xcf/0xe0
[ 242.230268][ C0] common_startup_64+0x12c/0x138
[ 242.230570][ C0] </TASK>
[ 242.230757][ C0] Modules linked in: [last unloaded: cifs]
[ 242.231113][ C0] ---[ end trace 0000000000000000 ]---
[ 242.231443][ C0] RIP: 0010:__lock_acquire+0x4f0/0x3c30
[ 242.231778][ C0] Code: 84 24 40 01 00 00 4c 89 f7 41 89 46 34 e8 e8 27 ff ff 48 ba 00 00 00 00 00 fc ff df 48 8d b8 c4 00 00 00 48 89 f9 48 c1 e9 03 <0f> b6 14 11 48 89 f9 83 e1 07 38 ca 7f 08 84 d2 0f 85 b6 29 00 00
[ 242.232952][ C0] RSP: 0018:ff1100006c009148 EFLAGS: 00010007
[ 242.233322][ C0] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000018
[ 242.233800][ C0] RDX: dffffc0000000000 RSI: 0000000000000004 RDI: 00000000000000c4
[ 242.234277][ C0] RBP: 0000000000000000 R08: 0000000000000001 R09: ffe21c000d83d141
[ 242.234756][ C0] R10: ff1100006c1e8a0b R11: 0000000000000017 R12: 0000000000000000
[ 242.235239][ C0] R13: ffffffff8502e6c0 R14: ffffffff8502f150 R15: 00000000000424e4
[ 242.235721][ C0] FS: 0000000000000000(0000) GS:ff1100006c000000(0000) knlGS:0000000000000000
[ 242.236257][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 242.236655][ C0] CR2: 00007ffd0d2666b8 CR3: 0000000010002002 CR4: 0000000000771ef0
[ 242.237140][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 242.237621][ C0] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[ 242.238101][ C0] PKRU: 55555554
[ 242.238317][ C0] Kernel panic - not syncing: Fatal exception in interrupt
[ 242.239006][ C0] Kernel Offset: disabled
[ 242.239320][ C0] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>
>
> Any thoughts on his patch? See below (and attached)
>
> Commit ef7134c7fc48 ("smb: client: Fix use-after-free of network
> namespace.")
> fixed a netns UAF by manually enabled socket refcounting
> (sk->sk_net_refcnt=1 and sock_inuse_add(net, 1)).
>
> The reason the patch worked for that bug was because we now hold
> references to the netns (get_net_track() gets a ref internally)
> and they're properly released (internally, on __sk_destruct()),
> but only because sk->sk_net_refcnt was set.
>
> Problem:
> (this happens regardless of CONFIG_NET_NS_REFCNT_TRACKER and regardless
> if init_net or other)
>
> Setting sk->sk_net_refcnt=1 *manually* and *after* socket creation is not
> only out of cifs scope, but also technically wrong -- it's set conditionally
> based on user (=1) vs kernel (=0) sockets. And net/ implementations
> seem to base their user vs kernel space operations on it.
>
> e.g. upon TCP socket close, the TCP timers are not cleared because
> sk->sk_net_refcnt=1:
> (cf. commit 151c9c724d05 ("tcp: properly terminate timers for
> kernel sockets"))
>
> net/ipv4/tcp.c:
> void tcp_close(struct sock *sk, long timeout)
> {
> lock_sock(sk);
> __tcp_close(sk, timeout);
> release_sock(sk);
> if (!sk->sk_net_refcnt)
> inet_csk_clear_xmit_timers_sync(sk);
> sock_put(sk);
> }
>
> Which will throw a lockdep warning and then, as expected, deadlock on
I wondered how the deadlock happens when I read this, but it seems this
'deadlock' means literally 'dead' (freed) lock, not something like ABBA
deadlock.
> tcp_write_timer().
>
> A way to reproduce this is by running the reproducer from ef7134c7fc48
> and then 'rmmod cifs'. A few seconds later, the deadlock/lockdep
> warning shows up.
>
> Fix:
> We shouldn't mess with socket internals ourselves, so do not set
> sk_net_refcnt manually.
>
> Also change __sock_create() to sock_create_kern() for explicitness.
>
> As for non-init_net network namespaces, we deal with it the best way
> we can -- hold an extra netns reference for server->ssocket and drop it
> when it's released. This ensures that the netns still exists whenever
> we need to create/destroy server->ssocket, but is not directly tied to
> it.
>
> Fixes: ef7134c7fc48 ("smb: client: Fix use-after-free of network
> namespace.")
>
