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Commit 8769f610 authored by Vasily Gorbik's avatar Vasily Gorbik
Browse files

s390/process: avoid potential reading of freed stack 



With THREAD_INFO_IN_TASK (which is selected on s390) task's stack usage
is refcounted and should always be protected by get/put when touching
other task's stack to avoid race conditions with task's destruction code.

Fixes: d5c352cd ("s390: move thread_info into task_struct")
Cc: stable@vger.kernel.org # v4.10+
Acked-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent f45f7b5b

arch/s390/kernel/process.c

+16 −6
Original line number Diff line number Diff line
@@ -184,20 +184,30 @@ unsigned long get_wchan(struct task_struct *p) 


	if (!p || p == current || p->state == TASK_RUNNING || !task_stack_page(p))

		return 0;



	if (!try_get_task_stack(p))

		return 0;



	low = task_stack_page(p);

	high = (struct stack_frame *) task_pt_regs(p);

	sf = (struct stack_frame *) p->thread.ksp;

	if (sf <= low || sf > high)

		return 0;

	if (sf <= low || sf > high) {

		return_address = 0;

		goto out;

	}

	for (count = 0; count < 16; count++) {

		sf = (struct stack_frame *) sf->back_chain;

		if (sf <= low || sf > high)

			return 0;

		if (sf <= low || sf > high) {

			return_address = 0;

			goto out;

		}

		return_address = sf->gprs[8];

		if (!in_sched_functions(return_address))

			return return_address;

			goto out;

	}

	return 0;

out:

	put_task_stack(p);

	return return_address;

}



unsigned long arch_align_stack(unsigned long sp)