Hi!
The __apply_to_page_range() function is also used to change and/or allocate page-table pages in the vmalloc area of the address space. Make sure these changes get synchronized to other page-tables in the system by calling arch_sync_kernel_mappings() when necessary.
There's no description here of the user-visible effects of the bug. Please always provide this, especially when proposing a -stable backport. Take pity upon all the downstream kernel maintainers who are staring at this wondering whether they should risk adding it to their kernels.
The impact appears limited to x86-32, where apply_to_page_range may miss updating the PMD. That leads to explosions in drivers like
Is this alone supposed to fix my problems with graphics on Thinkpad X60? Let me try...
Best regards, Pavel