[PATCH] arm64: fault: Route pte translation faults via do_translation_fault

[Catalin Marinas]

On Fri, Sep 29, 2017 at 12:27:41PM +0100, Will Deacon wrote:
> We currently route pte translation faults via do_page_fault, which elides
> the address check against TASK_SIZE before invoking the mm fault handling
> code. However, this can cause issues with the path walking code in
> conjunction with our word-at-a-time implementation because
> load_unaligned_zeropad can end up faulting in kernel space if it reads
> across a page boundary and runs into a page fault (e.g. by attempting to
> read from a guard region).
> 
> In the case of such a fault, load_unaligned_zeropad has registered a
> fixup to shift the valid data and pad with zeroes, however the abort is
> reported as a level 3 translation fault and we dispatch it straight to
> do_page_fault, despite it being a kernel address. This results in calling
> a sleeping function from atomic context:
> 
>   BUG: sleeping function called from invalid context at arch/arm64/mm/fault.c:313
>   in_atomic(): 0, irqs_disabled(): 0, pid: 10290
>   Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>   [...]
>   [<ffffff8e016cd0cc>] ___might_sleep+0x134/0x144
>   [<ffffff8e016cd158>] __might_sleep+0x7c/0x8c
>   [<ffffff8e016977f0>] do_page_fault+0x140/0x330
>   [<ffffff8e01681328>] do_mem_abort+0x54/0xb0
>   Exception stack(0xfffffffb20247a70 to 0xfffffffb20247ba0)
>   [...]
>   [<ffffff8e016844fc>] el1_da+0x18/0x78
>   [<ffffff8e017f399c>] path_parentat+0x44/0x88
>   [<ffffff8e017f4c9c>] filename_parentat+0x5c/0xd8
>   [<ffffff8e017f5044>] filename_create+0x4c/0x128
>   [<ffffff8e017f59e4>] SyS_mkdirat+0x50/0xc8
>   [<ffffff8e01684e30>] el0_svc_naked+0x24/0x28
>   Code: 36380080 d5384100 f9400800 9402566d (d4210000)
>   ---[ end trace 2d01889f2bca9b9f ]---
> 
> Fix this by dispatching all translation faults to do_translation_faults,
> which avoids invoking the page fault logic for faults on kernel addresses.
> 
> Cc: <stable at vger.kernel.org>
> Reported-by: Ankit Jain <ankijain at codeaurora.org>
> Signed-off-by: Will Deacon <will.deacon at arm.com>

Applied. Thanks.

-- 
Catalin