Commit-ID: c6c314a613cd7d03fb97713e0d642b493de42e69 Gitweb: http://git.kernel.org/tip/c6c314a613cd7d03fb97713e0d642b493de42e69 Author: Andy Lutomirski <[email protected]> AuthorDate: Thu, 15 Sep 2016 22:45:43 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 16 Sep 2016 09:18:53 +0200
sched/core: Add try_get_task_stack() and put_task_stack() 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 <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Jann Horn <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- include/linux/sched.h | 16 ++++++++++++++++ init/Kconfig | 3 +++ 2 files changed, 19 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index a287e8b..a958672 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3094,11 +3094,19 @@ static inline struct thread_info *task_thread_info(struct task_struct *task) { 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; @@ -3134,6 +3142,14 @@ static inline unsigned long *end_of_stack(struct task_struct *p) } #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) diff --git a/init/Kconfig b/init/Kconfig index ec8d438..3b9a47f 100644 --- 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
