linux-kernel - Re: [PATCH] ia64/err-inject: Use get_user_pages

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Date:   Tue, 27 Feb 2018 09:16:09 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     akpm@...ux-foundation.org, tony.luck@...el.com,
        fenghua.yu@...el.com
Cc:     linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] ia64/err-inject: Use get_user_pages_fast()

Andrew, if you're ok with the patch below, could it be routed
your way?

Thanks,
Davidlohr

On Mon, 22 Jan 2018, Davidlohr Bueso wrote:

>At the point of sysfs callback, the call to gup is
>done without mmap_sem (or any lock for that matter).
>This is racy. As such, use the get_user_pages_fast()
>alternative and safely avoid taking the lock, if possible.
>
>Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
>---
> arch/ia64/kernel/err_inject.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/ia64/kernel/err_inject.c b/arch/ia64/kernel/err_inject.c
>index 85bba43e7d5d..658a8e06a69b 100644
>--- a/arch/ia64/kernel/err_inject.c
>+++ b/arch/ia64/kernel/err_inject.c
>@@ -142,7 +142,7 @@ store_virtual_to_phys(struct device *dev, struct device_attribute *attr,
> 	u64 virt_addr=simple_strtoull(buf, NULL, 16);
> 	int ret;
>
>-	ret = get_user_pages(virt_addr, 1, FOLL_WRITE, NULL, NULL);
>+	ret = get_user_pages_fast(virt_addr, 1, FOLL_WRITE, NULL);
> 	if (ret<=0) {
> #ifdef ERR_INJ_DEBUG
> 		printk("Virtual address %lx is not existing.\n",virt_addr);
>-- 
>2.13.6
>