6.16-stable review patch. If anyone has any objections, please let me know.
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From: Waiman Long longman@redhat.com
commit dfb36e4a8db0cd56f92d4cb445f54e85a9b40897 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/futex/futex.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -321,13 +321,13 @@ static __always_inline int futex_put_val { 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; }