| From aa7c69e62fd7af740b7c599df342c2f5d22ae8c6 Mon Sep 17 00:00:00 2001 |
| From: Vasily Gorbik <gor@linux.ibm.com> |
| Date: Tue, 13 Aug 2019 20:11:08 +0200 |
| Subject: [PATCH] s390/process: avoid potential reading of freed stack |
| |
| 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: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c |
| index 63873aa6693f..9f2727bf3cbe 100644 |
| --- a/arch/s390/kernel/process.c |
| +++ b/arch/s390/kernel/process.c |
| @@ -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) |
| -- |
| 2.7.4 |
| |