On Tue, 26 Jan 2016, Will Deacon wrote:
> From 57adec866c0440976c96a4b8f5b59fb411b1cacb Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Mika=20Penttil=C3=A4?= <mika.pentt...@nextfour.com>
> Date: Tue, 26 Jan 2016 15:47:25 +0000
> Subject: [PATCH] arm64: mm: avoid calling apply_to_page_range on empty range
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>
> Calling apply_to_page_range with an empty range results in a BUG_ON
> from the core code. This can be triggered by trying to load the st_drv
> module with CONFIG_DEBUG_SET_MODULE_RONX enabled:
>
> kernel BUG at mm/memory.c:1874!
> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 3 PID: 1764 Comm: insmod Not tainted 4.5.0-rc1+ #2
> Hardware name: ARM Juno development board (r0) (DT)
> task: ffffffc9763b8000 ti: ffffffc975af8000 task.ti: ffffffc975af8000
> PC is at apply_to_page_range+0x2cc/0x2d0
> LR is at change_memory_common+0x80/0x108
>
> This patch fixes the issue by making change_memory_common (called by the
> set_memory_* functions) a NOP when numpages == 0, therefore avoiding the
> erroneous call to apply_to_page_range and bringing us into line with x86
> and s390.
>
> Cc: <sta...@vger.kernel.org>
> Reviewed-by: Laura Abbott <labb...@redhat.com>
> Acked-by: David Rientjes <rient...@google.com>
> Signed-off-by: Mika Penttilä <mika.pentt...@nextfour.com>
> Signed-off-by: Will Deacon <will.dea...@arm.com>
> ---
> arch/arm64/mm/pageattr.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 3571c7309c5e..cf6240741134 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -57,6 +57,9 @@ static int change_memory_common(unsigned long addr, int
> numpages,
> if (end < MODULES_VADDR || end >= MODULES_END)
> return -EINVAL;
>
> + if (!numpages)
> + return 0;
> +
> data.set_mask = set_mask;
> data.clear_mask = clear_mask;
>
LGTM, I think this issue goes back to 3.17 due to commit 11d91a770f1f
("arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support") so perhaps annotate
the sta...@vger.kernel.org for 3.17+.
