From: Vasily Gorbik gor@linux.ibm.com
commit 8769f610fe6d473e5e8e221709c3ac402037da6c upstream.
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: d5c352cdd022 ("s390: move thread_info into task_struct") Cc: stable@vger.kernel.org # v4.10+ Acked-by: Ilya Leoshkevich iii@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/s390/kernel/process.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
--- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -185,20 +185,30 @@ unsigned long get_wchan(struct task_stru
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)