[PATCH v4 0/5] serial: fix console lifetime bugs on failed bind and removal

[Karl Mehltretter <kmehltretter@gmail.com>]

This series fixes four serial/tty error-path bugs and an i.MX console
port-table lifetime bug. The fixes were found with failslab fail-nth sweeps
and sysfs bind/unbind sequences under KASAN on QEMU's raspi1ap and
mcimx6ul-evk machines.

Patches 1-4 fix shared serial/tty core code. They move fallible allocations
before console registration, clear pointers after uart_driver registration
fails, and make a non-NULL tty cdev slot mean that the cdev is live.

Patch 5 clears i.MX's devm-allocated port-table entry after failed probe and
removal. It keeps the entry valid through console unregistration, rejects
duplicate lines and serializes table updates against other port probes.

Validation includes fail-nth sweeps on both boards. The i.MX tests also
cover the sibling-probe race, sequential unbind/rebind and
CONFIG_PROVE_LOCKING=y.

Changes in v4:
- No code changes. v3 was accidentally sent as individual mails.
  Resending as a single thread.

Changes in v3:
- Drop Cc: stable from patches 1-4.
- Patch 1: remove redundant uport->name clearing and credit Sashiko's report
  with Reported-by and Closes trailers.
- Split v2 patch 3 into two patches with corresponding Fixes tags.
- Shorten the changelogs.
- Patch 5: use scoped guards, reject occupied slots, remove the unnecessary
  line variable, document the console-callback locking constraint and add a
  backport note.

Changes in v2:
- Patch 4: serialize port registration and removal with imx_uart_ports[]
  updates to close the reported sibling-probe race.
- Patches 1-3 are unchanged.

v3: https://lore.kernel.org/r/20260731180343.10818-1-kmehltretter@gmail.com
v2: https://lore.kernel.org/r/20260719221014.44354-1-kmehltretter@gmail.com
v1: https://lore.kernel.org/r/20260719160812.35407-1-kmehltretter@gmail.com

Karl Mehltretter (5):
  serial: core: do fallible allocations before the console can be
    registered
  serial: core: clear freed pointers on uart_register_driver() failure
  tty: skip cdev_del() when no cdev is registered
  tty: clear cdev pointer after cdev_add() failure
  serial: imx: serialize imx_uart_ports[] lifetime

 drivers/tty/serial/imx.c         | 20 +++++++++++++++++---
 drivers/tty/serial/serial_core.c | 32 ++++++++++++++++++--------------
 drivers/tty/tty_io.c             |  6 ++++--
 3 files changed, 39 insertions(+), 19 deletions(-)

-- 
2.53.0