| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 076/162] sched/core: Add try_get_task_stack() and put_task_stack() | Date | Thu, 19 Dec 2019 19:33:04 +0100 |
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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.git.luto@kernel.org 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
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