On 29/05/2026 10:34, Ard Biesheuvel wrote: > On Fri, 29 May 2026, at 10:29, Kevin Brodsky wrote: >> On 26/05/2026 19:59, Ard Biesheuvel wrote: >>> From: Ard Biesheuvel <[email protected]> >>> >>> The linear aliases of the kernel text and rodata are mapped read-only in >>> the linear map as well. Given that the contents of these regions are >>> mostly identical to the version in the loadable image, mapping them >>> read-only and leaving their contents visible is a reasonable hardening >>> measure. >>> >>> Data and bss, however, are now also mapped read-only but the contents of >>> these regions are more likely to contain data that we'd rather not leak. >>> So let's unmap these entirely in the linear map when the kernel is >>> running normally. >>> >>> When going into hibernation or waking up from it, these regions need to >>> be mapped, so map the region initially, and toggle the valid bit so >>> map/unmap the region as needed. (While the hibernation snapshot logic >>> seems able to map inaccessible pages as needed, it currently disregards >>> non-present pages entirely.) >> I'm not sure I understand this, is there something wrong with the >> kernel_page_present() check in safe_copy_page()? >> > No. If the hibernate code decides to snapshot a page and it is not mapped, > safe_copy_page() will do the right thing and map it on demand. > > The problem is that pages belonging to the kernel image are marked as > PageReserved, and so the hibernation logic will not even consider the > pages for snapshotting if they are not mapped.
Right I see the check in saveable_page() now. Maybe it would be worth spelling it out in the commit message (hibernation logic ignores non-present Reserved pages). - Kevin
