Improper Resource Locking Affecting kernel-rt-debug-kvm package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-kvm package and not the kernel-rt-debug-kvm package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

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

dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries_lock

__dma_entry_alloc_check_leak() calls into printk -> serial console output (qcom geni) and grabs port->lock under free_entries_lock spin lock, which is a reverse locking dependency chain as qcom_geni IRQ handler can call into dma-debug code and grab free_entries_lock under port->lock.

Move __dma_entry_alloc_check_leak() call out of free_entries_lock scope so that we don't acquire serial console's port->lock under it.

Trimmed-down lockdep splat:

The existing dependency chain (in reverse order) is:

           -> #2 (free_entries_lock){-.-.}-{2:2}:
    _raw_spin_lock_irqsave+0x60/0x80
    dma_entry_alloc+0x38/0x110
    debug_dma_map_page+0x60/0xf8
    dma_map_page_attrs+0x1e0/0x230
    dma_map_single_attrs.constprop.0+0x6c/0xc8
    geni_se_rx_dma_prep+0x40/0xcc
    qcom_geni_serial_isr+0x310/0x510
    __handle_irq_event_percpu+0x110/0x244
    handle_irq_event_percpu+0x20/0x54
    handle_irq_event+0x50/0x88
    handle_fasteoi_irq+0xa4/0xcc
    handle_irq_desc+0x28/0x40
    generic_handle_domain_irq+0x24/0x30
    gic_handle_irq+0xc4/0x148
    do_interrupt_handler+0xa4/0xb0
    el1_interrupt+0x34/0x64
    el1h_64_irq_handler+0x18/0x24
    el1h_64_irq+0x64/0x68
    arch_local_irq_enable+0x4/0x8
    ____do_softirq+0x18/0x24
    ...

       -> #1 (&port_lock_key){-.-.}-{2:2}:
_raw_spin_lock_irqsave+0x60/0x80
qcom_geni_serial_console_write+0x184/0x1dc
console_flush_all+0x344/0x454
console_unlock+0x94/0xf0
vprintk_emit+0x238/0x24c
vprintk_default+0x3c/0x48
vprintk+0xb4/0xbc
_printk+0x68/0x90
register_console+0x230/0x38c
uart_add_one_port+0x338/0x494
qcom_geni_serial_probe+0x390/0x424
platform_probe+0x70/0xc0
really_probe+0x148/0x280
__driver_probe_device+0xfc/0x114
driver_probe_device+0x44/0x100
__device_attach_driver+0x64/0xdc
bus_for_each_drv+0xb0/0xd8
__device_attach+0xe4/0x140
device_initial_probe+0x1c/0x28
bus_probe_device+0x44/0xb0
device_add+0x538/0x668
of_device_add+0x44/0x50
of_platform_device_create_pdata+0x94/0xc8
of_platform_bus_create+0x270/0x304
of_platform_populate+0xac/0xc4
devm_of_platform_populate+0x60/0xac
geni_se_probe+0x154/0x160
platform_probe+0x70/0xc0
...

       -> #0 (console_owner){-...}-{0:0}:
__lock_acquire+0xdf8/0x109c
lock_acquire+0x234/0x284
console_flush_all+0x330/0x454
console_unlock+0x94/0xf0
vprintk_emit+0x238/0x24c
vprintk_default+0x3c/0x48
vprintk+0xb4/0xbc
_printk+0x68/0x90
dma_entry_alloc+0xb4/0x110
debug_dma_map_sg+0xdc/0x2f8
__dma_map_sg_attrs+0xac/0xe4
dma_map_sgtable+0x30/0x4c
get_pages+0x1d4/0x1e4 [msm]
msm_gem_pin_pages_locked+0x38/0xac [msm]
msm_gem_pin_vma_locked+0x58/0x88 [msm]
msm_ioctl_gem_submit+0xde4/0x13ac [msm]
drm_ioctl_kernel+0xe0/0x15c
drm_ioctl+0x2e8/0x3f4
vfs_ioctl+0x30/0x50
...

Chain exists of: console_owner --> &port_lock_key --> free_entries_lock

Possible unsafe locking scenario:

    CPU0                    CPU1
    ----                    ----

lock(free_entries_lock); lock(&port_lock_key); lock(free_entries_lock); lock(console_owner);

            *** DEADLOCK ***

Call trace: dump_backtrace+0xb4/0xf0 show_stack+0x20/0x30 dump_stack_lvl+0x60/0x84 dump_stack+0x18/0x24 print_circular_bug+0x1cc/0x234 check_noncircular+0x78/0xac __lock_acquire+0xdf8/0x109c lock_acquire+0x234/0x284 console_flush_all+0x330/0x454 consol ---truncated---

• https://access.redhat.com/security/cve/CVE-2023-52516
• https://git.kernel.org/stable/c/ac0d068099349cbca3d93f2e3b15bb329364b08c
• https://git.kernel.org/stable/c/be8f49029eca3efbad0d74dbff3cb9129994ffab
• https://git.kernel.org/stable/c/c79300599923daaa30f417c75555d5566b3d31ae
• https://git.kernel.org/stable/c/fb5a4315591dae307a65fc246ca80b5159d296e1
• https://git.kernel.org/stable/c/fe2b811a02c3244ebf6059039e4a9e715e26a9e3