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    Subject[PATCH 4.19 124/323] task_stack: Fix end_of_stack() for architectures with upwards-growing stack
    Date
    From: Helge Deller <deller@gmx.de>

    [ Upstream commit 9cc2fa4f4a92ccc6760d764e7341be46ee8aaaa1 ]

    The function end_of_stack() returns a pointer to the last entry of a
    stack. For architectures like parisc where the stack grows upwards
    return the pointer to the highest address in the stack.

    Without this change I faced a crash on parisc, because the stackleak
    functionality wrote STACKLEAK_POISON to the lowest address and thus
    overwrote the first 4 bytes of the task_struct which included the
    TIF_FLAGS.

    Signed-off-by: Helge Deller <deller@gmx.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/sched/task_stack.h | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/include/linux/sched/task_stack.h b/include/linux/sched/task_stack.h
    index 6a841929073f9..4f099d3fed3a9 100644
    --- a/include/linux/sched/task_stack.h
    +++ b/include/linux/sched/task_stack.h
    @@ -25,7 +25,11 @@ static inline void *task_stack_page(const struct task_struct *task)

    static inline unsigned long *end_of_stack(const struct task_struct *task)
    {
    +#ifdef CONFIG_STACK_GROWSUP
    + return (unsigned long *)((unsigned long)task->stack + THREAD_SIZE) - 1;
    +#else
    return task->stack;
    +#endif
    }

    #elif !defined(__HAVE_THREAD_FUNCTIONS)
    --
    2.33.0


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