Subject: CVE-2021-47041: nvmet-tcp: fix incorrect locking in state_change sk callback

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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+0x170/0x170
 inet_shutdown+0x189/0x300
 __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
 ? new_sync_read+0x600/0x600
 ? lock_acquire+0x1ca/0x480
 ? rcu_read_unlock+0x40/0x40
 ? lock_is_held_type+0x9a/0x110
 vfs_write+0x5c0/0x870
 ksys_write+0xf9/0x1d0
 ? __ia32_sys_read+0xa0/0xa0
 ? lockdep_hardirqs_on_prepare.part.0+0x198/0x340
 ? syscall_enter_from_user_mode+0x27/0x70
 do_syscall_64+0x33/0x40
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The Linux kernel CVE team has assigned CVE-2021-47041 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.0 with commit 872d26a391da and fixed in 5.4.119 with commit 999d606a820c
	Issue introduced in 5.0 with commit 872d26a391da and fixed in 5.10.37 with commit 60ade0d56b06
	Issue introduced in 5.0 with commit 872d26a391da and fixed in 5.11.21 with commit 06beaa1a9f6e
	Issue introduced in 5.0 with commit 872d26a391da and fixed in 5.12.4 with commit 906c538340dd
	Issue introduced in 5.0 with commit 872d26a391da and fixed in 5.13 with commit b5332a9f3f3d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47041
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/nvme/target/tcp.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/999d606a820c36ae9b9e9611360c8b3d8d4bb777
	https://git.kernel.org/stable/c/60ade0d56b06537a28884745059b3801c78e03bc
	https://git.kernel.org/stable/c/06beaa1a9f6e501213195e47c30416032fd2bbd5
	https://git.kernel.org/stable/c/906c538340dde6d891df89fe7dac8eaa724e40da
	https://git.kernel.org/stable/c/b5332a9f3f3d884a1b646ce155e664cc558c1722