[PATCH v2] futex: Use user_write_access_begin/_end() in futex_put_value()

[Waiman Long <longman@redhat.com>]

Commit cec199c5e39b ("futex: Implement FUTEX2_NUMA") introduces a new
futex_put_value() helper function to write a value to the given user
address. However, it uses user_read_access_begin() before the write.
For arches that differentiate between read and write accesses, like
powerpc, futex_put_value() fails with a -EFAULT return value.  Fix that
by using the user_write_access_begin/user_write_access_end() pair.

Fixes: cec199c5e39b ("futex: Implement FUTEX2_NUMA")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/futex/futex.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index c74eac572acd..ebe9e755b3b5 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -319,10 +319,10 @@ static __always_inline int futex_put_value(u32 val, u32 __user *to)
 {
 	if (can_do_masked_user_access())
 		to = masked_user_access_begin(to);
-	else if (!user_read_access_begin(to, sizeof(*to)))
+	else if (!user_write_access_begin(to, sizeof(*to)))
 		return -EFAULT;
 	unsafe_put_user(val, to, Efault);
-	user_read_access_end();
+	user_write_access_end();
 	return 0;
 Efault:
 	user_read_access_end();
-- 
2.50.1