As so often with virtio-mem changes that mess with common MM infrastructure, this might be a good candiate to go via Andrew's tree. -- After removing /dev/kmem, sanitizing /proc/kcore and handling /dev/mem, this series tackles the last sane way how a VM could accidentially access logically unplugged memory managed by a virtio-mem device: /proc/vmcore When dumping memory via "makedumpfile", PG_offline pages, used by virtio-mem to flag logically unplugged memory, are already properly excluded; however, especially when accessing/copying /proc/vmcore "the usual way", we can still end up reading logically unplugged memory part of a virtio-mem device. Patch #1-#3 are cleanups. Patch #4 extends the existing oldmem_pfn_is_ram mechanism. Patch #5-#7 are virtio-mem refactorings for patch #8, which implements the virtio-mem logic to query the state of device blocks. Patch #8: " Although virtio-mem currently supports reading unplugged memory in the hypervisor, this will change in the future, indicated to the device via a new feature flag. We similarly sanitized /proc/kcore access recently. [...] Distributions that support virtio-mem+kdump have to make sure that the virtio_mem module will be part of the kdump kernel or the kdump initrd; dracut was recently [2] extended to include virtio-mem in the generated initrd. As long as no special kdump kernels are used, this will automatically make sure that virtio-mem will be around in the kdump initrd and sanitize /proc/vmcore access -- with dracut. " This is the last remaining bit to support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE [3] in the Linux implementation of virtio-mem. Note: this is best-effort. We'll never be able to control what runs inside the second kernel, really, but we also don't have to care: we only care about sane setups where we don't want our VM getting zapped once we touch the wrong memory location while dumping. While we usually expect sane setups to use "makedumfile", nothing really speaks against just copying /proc/vmcore, especially in environments where HWpoisioning isn't typically expected. Also, we really don't want to put all our trust completely on the memmap, so sanitizing also makes sense when just using "makedumpfile". [1] https://lkml.kernel.org/r/20210526093041.8800-1-david@xxxxxxxxxx [2] https://github.com/dracutdevs/dracut/pull/1157 [3] https://lists.oasis-open.org/archives/virtio-comment/202109/msg00021.html v1 -> v2: - "x86/xen: simplify xen_oldmem_pfn_is_ram()" -- Simplify even more - "x86/xen: print a warning when HVMOP_get_mem_type fails" -- Added - "virtio-mem: kdump mode to sanitize /proc/vmcore access" -- Fix wrong range check Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Jason Wang <jasowang@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: kexec@xxxxxxxxxxxxxxxxxxx Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx David Hildenbrand (9): x86/xen: update xen_oldmem_pfn_is_ram() documentation x86/xen: simplify xen_oldmem_pfn_is_ram() x86/xen: print a warning when HVMOP_get_mem_type fails proc/vmcore: let pfn_is_ram() return a bool proc/vmcore: convert oldmem_pfn_is_ram callback to more generic vmcore callbacks virtio-mem: factor out hotplug specifics from virtio_mem_init() into virtio_mem_init_hotplug() virtio-mem: factor out hotplug specifics from virtio_mem_probe() into virtio_mem_init_hotplug() virtio-mem: factor out hotplug specifics from virtio_mem_remove() into virtio_mem_deinit_hotplug() virtio-mem: kdump mode to sanitize /proc/vmcore access arch/x86/kernel/aperture_64.c | 13 +- arch/x86/xen/mmu_hvm.c | 37 ++--- drivers/virtio/virtio_mem.c | 297 ++++++++++++++++++++++++---------- fs/proc/vmcore.c | 105 ++++++++---- include/linux/crash_dump.h | 26 ++- 5 files changed, 333 insertions(+), 145 deletions(-) base-commit: 9e1ff307c779ce1f0f810c7ecce3d95bbae40896 -- 2.31.1
