On Mon, Jul 18, 2022 at 03:32:40PM +0200, Alexander Gordeev wrote:
> +++ b/arch/s390/kernel/crash_dump.c
> @@ -53,6 +53,7 @@ struct save_area {
> };
>
> static LIST_HEAD(dump_save_areas);
I'd suggest you need a mutex here so that simultaneous calls to
copy_to_user_real() don't corrupt each others data.
> +static char memcpy_real_buf[PAGE_SIZE];
>
> /*
> * Allocate a save area
> @@ -179,23 +180,18 @@ int copy_oldmem_kernel(void *dst, unsigned long src, size_t count)
> static int copy_to_user_real(void __user *dest, unsigned long src, unsigned long count)
> {
> int offs = 0, size, rc;
> - char *buf;
>
> - buf = (char *)__get_free_page(GFP_KERNEL);
> - if (!buf)
> - return -ENOMEM;
> rc = -EFAULT;
> while (offs < count) {
> size = min(PAGE_SIZE, count - offs);
> - if (memcpy_real(buf, src + offs, size))
> + if (memcpy_real(memcpy_real_buf, src + offs, size))
> goto out;
> - if (copy_to_user(dest + offs, buf, size))
> + if (copy_to_user(dest + offs, memcpy_real_buf, size))
> goto out;
> offs += size;
> }
> rc = 0;
> out:
> - free_page((unsigned long)buf);
> return rc;
> }
>
> --
> 2.34.1
>
