From: David Woodhouse dwmw@amazon.co.uk
[ Upstream commit 6d712b9b3a58018259fb40ddd498d1f7dfa1f4ec ]
Commit dce1ca0525bf ("sched/scs: Reset task stack state in bringup_cpu()") ensured that the shadow call stack and KASAN poisoning were removed from a CPU's stack each time that CPU is brought up, not just once.
This is not incorrect. However, with parallel bringup the idle thread setup will happen at a different step. As a consequence the cleanup in bringup_cpu() would be too late.
Move the SCS/KASAN cleanup to the generic _cpu_up() function instead, which already ensures that the new CPU's stack is available, purely to allow for early failure. This occurs when the CPU to be brought up is in the CPUHP_OFFLINE state, which should correctly do the cleanup any time the CPU has been taken down to the point where such is needed.
Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Mark Rutland mark.rutland@arm.com Tested-by: Mark Rutland mark.rutland@arm.com Tested-by: Michael Kelley mikelley@microsoft.com Tested-by: Oleksandr Natalenko oleksandr@natalenko.name Tested-by: Helge Deller deller@gmx.de # parisc Tested-by: Guilherme G. Piccoli gpiccoli@igalia.com # Steam Deck Link: https://lore.kernel.org/r/20230512205257.027075560@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/cpu.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c index 393114c10c285..4191f17379d2f 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -590,12 +590,6 @@ static int bringup_cpu(unsigned int cpu) struct task_struct *idle = idle_thread_get(cpu); int ret;
- /* - * Reset stale stack state from the last time this CPU was online. - */ - scs_task_reset(idle); - kasan_unpoison_task_stack(idle); - /* * Some architectures have to walk the irq descriptors to * setup the vector space for the cpu which comes online. @@ -1372,6 +1366,12 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) ret = PTR_ERR(idle); goto out; } + + /* + * Reset stale stack state from the last time this CPU was online. + */ + scs_task_reset(idle); + kasan_unpoison_task_stack(idle); }
cpuhp_tasks_frozen = tasks_frozen;