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Subject[PATCH 4.14 219/496] ia64/err-inject: Use get_user_pages_fast()
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davidlohr Bueso <dave@stgolabs.net>

[ Upstream commit 69c907022a7d9325cdc5c9dd064571e445df9a47 ]

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@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/ia64/kernel/err_inject.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- 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
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);

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