The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: dfb36e4a8db0cd56f92d4cb445f54e85a9b40897 Gitweb: https://git.kernel.org/tip/dfb36e4a8db0cd56f92d4cb445f54e85a9b40897 Author: Waiman Long longman@redhat.com AuthorDate: Mon, 11 Aug 2025 10:11:47 -04:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Mon, 11 Aug 2025 17:53:21 +02:00

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 --- kernel/futex/futex.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index c74eac5..2cd5709 100644 --- 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; }