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

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Message-Id: <20180122172137.26849-1-dave@stgolabs.net>
Date:   Mon, 22 Jan 2018 09:21:37 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     tony.luck@...el.com, fenghua.yu@...el.com
Cc:     linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
        dave@...olabs.net, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH] ia64/err-inject: Use get_user_pages_fast()

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