futex: Use user_write_access_begin/_end() in futex_put_value()

Commit cec199c5e39b ("futex: Implement FUTEX2_NUMA") introduced the
futex_put_value() helper to write a value to the given user
address.

However, it uses user_read_access_begin() before the write. For
architectures that differentiate between read and write accesses, like
PowerPC, futex_put_value() fails with -EFAULT.

Fix that by using the user_write_access_begin/user_write_access_end() pair
instead.

Fixes: cec199c5e39b ("futex: Implement FUTEX2_NUMA")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250811141147.322261-1-longman@redhat.com

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index c74eac572acd7fd64efcf22cc5f4045312785a31..2cd57096c38e188835a17d6340d9c3bd2c6a354a 100644 (file)
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -319,13 +319,13 @@ 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();
+       user_write_access_end();
        return -EFAULT;
 }