On Sun, Jan 22, 2023 at 9:44 PM <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > The patch below does not apply to the 5.10-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to <stable@xxxxxxxxxxxxxxx>. That uninitialized reading is living in 5.10.y branch now https://github.com/gregkh/linux/blob/v5.10.162/io_uring/io_uring.c#L4989-L5017 If this: ret = import_single_range(RE AD, buf, sr->len, &iov, &msg.msg_iter); fails, this one (flags & MSG_WAITALL) may read an uninitialized variable because @flags is uninitialized. Fortunately, if import_single_range() fails, (ret < min_ret) is always true, so this: ret < min_ret || ((flags & MSG_WAITALL) will always short circuit. But no one tells the compiler if @ret is always less than @min_ret in that case. So it can't prove that @flags is never actually read. That still falls to undefined behavior anyway, the compiler may emit "ud2" or similar trap for that or behave randomly. IDK...
