From: Waiman Long Date: Mon, 11 Aug 2025 14:11:47 +0000 (-0400) Subject: futex: Use user_write_access_begin/_end() in futex_put_value() X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=dfb36e4a8db0cd56f92d4cb445f54e85a9b40897;p=users%2Fhch%2Fmisc.git 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 Signed-off-by: Thomas Gleixner 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 c74eac572acd..2cd57096c38e 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; }