lkml.org 
[lkml]   [2016]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v5 28/32] sched: Add try_get_task_stack() and put_task_stack()
    Date
    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>
    ---
    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 4108b4880b86..18bef18fef88 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -3063,11 +3063,19 @@ 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;
    @@ -3103,6 +3111,14 @@ 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 2cdf20e03b1f..8823df60d312 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().
    +
    menu "General setup"

    config BROKEN
    --
    2.7.4
    \
     
     \ /
      Last update: 2016-07-11 23:41    [W:4.867 / U:0.360 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site