Oracle Linux: (CVE-2021-47185) ELSA-2024-3618: kernel update

Description

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

tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc

When running ltp testcase(ltp/testcases/kernel/pty/pty04.c) with arm64, there is a soft lockup,

which look like this one:

Workqueue: events_unbound flush_to_ldisc

Call trace:

dump_backtrace+0x0/0x1ec

show_stack+0x24/0x30

dump_stack+0xd0/0x128

panic+0x15c/0x374

watchdog_timer_fn+0x2b8/0x304

__run_hrtimer+0x88/0x2c0

__hrtimer_run_queues+0xa4/0x120

hrtimer_interrupt+0xfc/0x270

arch_timer_handler_phys+0x40/0x50

handle_percpu_devid_irq+0x94/0x220

__handle_domain_irq+0x88/0xf0

gic_handle_irq+0x84/0xfc

el1_irq+0xc8/0x180

slip_unesc+0x80/0x214 [slip]

tty_ldisc_receive_buf+0x64/0x80

tty_port_default_receive_buf+0x50/0x90

flush_to_ldisc+0xbc/0x110

process_one_work+0x1d4/0x4b0

worker_thread+0x180/0x430

kthread+0x11c/0x120

In the testcase pty04, The first process call the write syscall to send

data to the pty master. At the same time, the workqueue will do the

flush_to_ldisc to pop data in a loop until there is no more data left.

When the sender and workqueue running in different core, the sender sends

data fastly in full time which will result in workqueue doing work in loop

for a long time and occuring softlockup in flush_to_ldisc with kernel

configured without preempt. So I add need_resched check and cond_resched

in the flush_to_ldisc loop to avoid it.