[PATCH v7 0/2] serial: core: fix baud rate fallback loop and baud_base overflow

[Hui Peng <benquike@gmail.com>]

This series addresses two issues in serial core:
1. Division-by-zero WARN/Oops during baud rate fallback in uart_get_baud_rate().
2. 32-bit unsigned overflow in uart_set_info() when multiplying new_info->baud_base by 16.

Note on v6 1/3:
Patch 1/3 from v6 ("serial: 8250: fix deadlock in serial8250_register_ports")
has been dropped. The hash_mutex race condition was originally found and
reproduced on Linux 6.18.14 (where guard(mutex)(&hash_mutex) was dropped
inside serial_get_or_create_irq_info() before serial_link_irq_chain() linked
the port). We did not realize that it was already fixed in mainline by
commit b339809edda1 ("serial: 8250: use guard()s"), which refactored to
serial_get_or_create_irq_info_locked() with guard(mutex)(&hash_mutex) moved
into serial_link_irq_chain(). Apologies for the noise in v6 1/3.

All remaining patches are ported to the latest tip of mainline (551c722f4080)
and dynamically verified in QEMU KVM with CONFIG_KASAN=y.

Changes in v7:
- Dropped patch 1/3 (already resolved in mainline).
- Clarified in cover letter that 1/3 was found and reproduced on 6.18.14 and
  we did not realize it was already fixed in mainline.
- Retained patch 1/2 and patch 2/2 using check_mul_overflow() as requested
  by Jiri Slaby.

Hui Peng (2):
  serial: core: fix baud rate fallback in uart_get_baud_rate()
  serial: core: reject baud_base values that overflow port->uartclk in
    uart_set_info()

 drivers/tty/serial/serial_core.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
-- 
2.47.3