sched/deadline: Fix warning in migrate_enable for boosted tasks

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

sched/deadline: Fix warning in migrate_enable for boosted tasks

When running the following command:

while true; do

stress-ng --cyclic 30 --timeout 30s --minimize --quiet

done

a warning is eventually triggered:

WARNING: CPU: 43 PID: 2848 at kernel/sched/deadline.c:794

setup_new_dl_entity+0x13e/0x180

...

Call Trace:

<TASK>

? show_trace_log_lvl+0x1c4/0x2df

? enqueue_dl_entity+0x631/0x6e0

? setup_new_dl_entity+0x13e/0x180

? __warn+0x7e/0xd0

? report_bug+0x11a/0x1a0

? handle_bug+0x3c/0x70

? exc_invalid_op+0x14/0x70

? asm_exc_invalid_op+0x16/0x20

enqueue_dl_entity+0x631/0x6e0

enqueue_task_dl+0x7d/0x120

__do_set_cpus_allowed+0xe3/0x280

__set_cpus_allowed_ptr_locked+0x140/0x1d0

__set_cpus_allowed_ptr+0x54/0xa0

migrate_enable+0x7e/0x150

rt_spin_unlock+0x1c/0x90

group_send_sig_info+0xf7/0x1a0

? kill_pid_info+0x1f/0x1d0

kill_pid_info+0x78/0x1d0

kill_proc_info+0x5b/0x110

__x64_sys_kill+0x93/0xc0

do_syscall_64+0x5c/0xf0

entry_SYSCALL_64_after_hwframe+0x6e/0x76

RIP: 0033:0x7f0dab31f92b

This warning occurs because set_cpus_allowed dequeues and enqueues tasks

with the ENQUEUE_RESTORE flag set. If the task is boosted, the warning

is triggered. A boosted task already had its parameters set by

rt_mutex_setprio, and a new call to setup_new_dl_entity is unnecessary,

hence the WARN_ON call.

Check if we are requeueing a boosted task and avoid calling

setup_new_dl_entity if that's the case.