CVE-2024-26998
Assigner: Linux
Published: 2024-05-01T05:28:25.905Z
State: PUBLISHED
descriptions: value: In the Linux kernel, the following vulnerability has been resolved:

serial: core: Clearing the circular buffer before NULLifying it

The circular buffer is NULLified in uart_tty_port_shutdown()
under the spin lock. However, the PM or other timer based callbacks
may still trigger after this event without knowning that buffer pointer
is not valid. Since the serial code is a bit inconsistent in checking
the buffer state (some rely on the head-tail positions, some on the
buffer pointer), it's better to have both aligned, i.e. buffer pointer
to be NULL and head-tail possitions to be the same, meaning it's empty.
This will prevent asynchronous calls to dereference NULL pointer as
reported recently in 8250 case:

  BUG: kernel NULL pointer dereference, address: 00000cf5
  Workqueue: pm pm_runtime_work
  EIP: serial8250_tx_chars (drivers/tty/serial/8250/8250_port.c:1809)
  ...
  ? serial8250_tx_chars (drivers/tty/serial/8250/8250_port.c:1809)
  __start_tx (drivers/tty/serial/8250/8250_port.c:1551)
  serial8250_start_tx (drivers/tty/serial/8250/8250_port.c:1654)
  serial_port_runtime_suspend (include/linux/serial_core.h:667 drivers/tty/serial/serial_port.c:63)
  __rpm_callback (drivers/base/power/runtime.c:393)
  ? serial_port_remove (drivers/tty/serial/serial_port.c:50)
  rpm_suspend (drivers/base/power/runtime.c:447)

The proposed change will prevent ->start_tx() to be called during
suspend on shut down port.
affected: product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 434beb66368d
lessThan: 7ae7104d5434
status: affected
versionType: git
version: 43066e32227e
lessThan: bb1118905e87
status: affected
versionType: git
version: 43066e32227e
lessThan: 9cf7ea2eeb74
status: affected
versionType: git
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 6.8
status: affected
version: 0
lessThan: 6.8
status: unaffected
versionType: custom
version: 6.6.29
lessThanOrEqual: 6.6.*
status: unaffected
versionType: custom
version: 6.8.8
lessThanOrEqual: 6.8.*
status: unaffected
versionType: custom
version: 6.9
lessThanOrEqual: *
status: unaffected
versionType: original_commit_for_fix
title: serial: core: Clearing the circular buffer before NULLifying it
x_generator: engine: bippy-d175d3acf727