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SubjectRe: [PATCH v2] stackdepot: ignore junk last entry in case of switch from user mode.
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On 10/11/2017 03:43 PM, Maninder Singh wrote:
> Issue observed on ARM.
>
> Whenever there is switch from user mode, we end up with invalid last entry
> with some user space address as below:-
>
> save_stack+0x40/0xec
> __set_page_owner+0x2c/0x64
> ....
> ....
> __handle_domain_irq+0x9c/0x130
> gic_handle_irq+0x40/0x80
> __irq_usr+0x4c/0x60
> 0xb6507818
>

Sounds like an ARM issue to me.

...

> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index f87d138..a045748 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -214,6 +214,13 @@ depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
> if (unlikely(trace->nr_entries == 0))
> goto fast_exit;
>
> + /*
> + * Ignore last entry if it belongs to user space

And if it belongs to module too. NACK.


> + * in case of switch from user mode.
> + */
> + if (!kernel_text_address(trace->entries[trace->nr_entries - 1]))
> + trace->nr_entries--;
> +
> hash = hash_stack(trace->entries, trace->nr_entries);
> bucket = &stack_table[hash & STACK_HASH_MASK];
>
>

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