On Fri, 23 Jan 2026 at 07:52, Anshuman Khandual <[email protected]> wrote: > > > > On 19/01/26 10:17 PM, Ard Biesheuvel wrote: > > From: Ard Biesheuvel <[email protected]> > > > > The linear aliases of the kernel text and rodata are mapped read-only as > > well. Given that the contents of these regions are mostly identical to > > the version in the loadable image, mapping them read-only 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. > > > > Only when going into hibernation or waking up from it do these regions > > need to be mapped, so take care of this using a PM notifier. > > Just curious - why do we need them mapped while going into or coming back > from the hibernation ? >
Because the kernel image is preserved/restored via the linear map. For some reason, it appears to be sufficient for this mapping to be read-only but unmapping it entirely results in failures to resume from hibernation.
