From: Andy Lutomirski luto@kernel.org
commit c6c314a613cd7d03fb97713e0d642b493de42e69 upstream.
There are a few places in the kernel that access stack memory belonging to a different task. Before we can start freeing task stacks before the task_struct is freed, we need a way for those code paths to pin the stack.
Signed-off-by: Andy Lutomirski luto@kernel.org Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: H. Peter Anvin hpa@zytor.com Cc: Jann Horn jann@thejh.net Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/sched.h | 16 ++++++++++++++++ init/Kconfig | 3 +++ 2 files changed, 19 insertions(+)
--- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2858,11 +2858,19 @@ static inline struct thread_info *task_t { return &task->thread_info; } + +/* + * When accessing the stack of a non-current task that might exit, use + * try_get_task_stack() instead. task_stack_page will return a pointer + * that could get freed out from under you. + */ static inline void *task_stack_page(const struct task_struct *task) { return task->stack; } + #define setup_thread_stack(new,old) do { } while(0) + static inline unsigned long *end_of_stack(const struct task_struct *task) { return task->stack; @@ -2898,6 +2906,14 @@ static inline unsigned long *end_of_stac }
#endif + +static inline void *try_get_task_stack(struct task_struct *tsk) +{ + return task_stack_page(tsk); +} + +static inline void put_task_stack(struct task_struct *tsk) {} + #define task_stack_end_corrupted(task) \ (*(end_of_stack(task)) != STACK_END_MAGIC)
--- a/init/Kconfig +++ b/init/Kconfig @@ -33,6 +33,9 @@ config THREAD_INFO_IN_TASK make this work, an arch will need to remove all thread_info fields except flags and fix any runtime bugs.
+ One subtle change that will be needed is to use try_get_task_stack() + and put_task_stack() in save_thread_stack_tsk() and get_wchan(). + menu "General setup"
config BROKEN