CVE-2021-47041

In the Linux kernel, the following vulnerability has been resolved:

nvmet-tcp: fix incorrect locking in state_change sk callback

We are not changing anything in the TCP connection state so

we should not take a write_lock but rather a read lock.

This caused a deadlock when running nvmet-tcp and nvme-tcp

on the same system, where state_change callbacks on the

host and on the controller side have causal relationship

and made lockdep report on this with blktests:

================================

WARNING: inconsistent lock state

5.12.0-rc3 #1 Tainted: G I

--------------------------------

inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-R} usage.

nvme/1324 [HC0[0]:SC0[0]:HE1:SE1] takes:

ffff888363151000 (clock-AF_INET){++-?}-{2:2}, at: nvme_tcp_state_change+0x21/0x150 [nvme_tcp]

{IN-SOFTIRQ-W} state was registered at:

__lock_acquire+0x79b/0x18d0

lock_acquire+0x1ca/0x480

_raw_write_lock_bh+0x39/0x80

nvmet_tcp_state_change+0x21/0x170 [nvmet_tcp]

tcp_fin+0x2a8/0x780

tcp_data_queue+0xf94/0x1f20

tcp_rcv_established+0x6ba/0x1f00

tcp_v4_do_rcv+0x502/0x760

tcp_v4_rcv+0x257e/0x3430

ip_protocol_deliver_rcu+0x69/0x6a0

ip_local_deliver_finish+0x1e2/0x2f0

ip_local_deliver+0x1a2/0x420

ip_rcv+0x4fb/0x6b0

__netif_receive_skb_one_core+0x162/0x1b0

process_backlog+0x1ff/0x770

__napi_poll.constprop.0+0xa9/0x5c0

net_rx_action+0x7b3/0xb30

__do_softirq+0x1f0/0x940

do_softirq+0xa1/0xd0

__local_bh_enable_ip+0xd8/0x100

ip_finish_output2+0x6b7/0x18a0

__ip_queue_xmit+0x706/0x1aa0

__tcp_transmit_skb+0x2068/0x2e20

tcp_write_xmit+0xc9e/0x2bb0

__tcp_push_pending_frames+0x92/0x310

inet_shutdown+0x158/0x300

__nvme_tcp_stop_queue+0x36/0x270 [nvme_tcp]

nvme_tcp_stop_queue+0x87/0xb0 [nvme_tcp]

nvme_tcp_teardown_admin_queue+0x69/0xe0 [nvme_tcp]

nvme_do_delete_ctrl+0x100/0x10c [nvme_core]

nvme_sysfs_delete.cold+0x8/0xd [nvme_core]

kernfs_fop_write_iter+0x2c7/0x460

new_sync_write+0x36c/0x610

vfs_write+0x5c0/0x870

ksys_write+0xf9/0x1d0

do_syscall_64+0x33/0x40

entry_SYSCALL_64_after_hwframe+0x44/0xae

irq event stamp: 10687

hardirqs last enabled at (10687): [<ffffffff9ec376bd>] _raw_spin_unlock_irqrestore+0x2d/0x40

hardirqs last disabled at (10686): [<ffffffff9ec374d8>] _raw_spin_lock_irqsave+0x68/0x90

softirqs last enabled at (10684): [<ffffffff9f000608>] __do_softirq+0x608/0x940

softirqs last disabled at (10649): [<ffffffff9cdedd31>] do_softirq+0xa1/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0

----

lock(clock-AF_INET);

<Interrupt>

lock(clock-AF_INET);

*** DEADLOCK ***

5 locks held by nvme/1324:

#0: ffff8884a01fe470 (sb_writers#4){.+.+}-{0:0}, at: ksys_write+0xf9/0x1d0

#1: ffff8886e435c090 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x216/0x460

#2: ffff888104d90c38 (kn->active#255){++++}-{0:0}, at: kernfs_remove_self+0x22d/0x330

#3: ffff8884634538d0 (&queue->queue_lock){+.+.}-{3:3}, at: nvme_tcp_stop_queue+0x52/0xb0 [nvme_tcp]

#4: ffff888363150d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_shutdown+0x59/0x300

stack backtrace:

CPU: 26 PID: 1324 Comm: nvme Tainted: G I 5.12.0-rc3 #1

Hardware name: Dell Inc. PowerEdge R640/06NR82, BIOS 2.10.0 11/12/2020

Call Trace:

dump_stack+0x93/0xc2

mark_lock_irq.cold+0x2c/0xb3

? verify_lock_unused+0x390/0x390

? stack_trace_consume_entry+0x160/0x160

? lock_downgrade+0x100/0x100

? save_trace+0x88/0x5e0

? _raw_spin_unlock_irqrestore+0x2d/0x40

mark_lock+0x530/0x1470

? mark_lock_irq+0x1d10/0x1d10

? enqueue_timer+0x660/0x660

mark_usage+0x215/0x2a0

__lock_acquire+0x79b/0x18d0

? tcp_schedule_loss_probe.part.0+0x38c/0x520

lock_acquire+0x1ca/0x480

? nvme_tcp_state_change+0x21/0x150 [nvme_tcp]

? rcu_read_unlock+0x40/0x40

? tcp_mtu_probe+0x1ae0/0x1ae0

? kmalloc_reserve+0xa0/0xa0

? sysfs_file_ops+0x170/0x170

_raw_read_lock+0x3d/0xa0

? nvme_tcp_state_change+0x21/0x150 [nvme_tcp]

nvme_tcp_state_change+0x21/0x150 [nvme_tcp]

? sysfs_file_ops

---truncated---