The data offset for a dax region needs to account for a reservation in the resource range. Otherwise, device-dax is allowing mappings directly into the memmap or device-info-block area with crash signatures like the following:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: [<ffffffff811ac851>] get_zone_device_page+0x11/0x30 Call Trace: follow_devmap_pmd+0x298/0x2c0 follow_page_mask+0x275/0x530 __get_user_pages+0xe3/0x750 __gfn_to_pfn_memslot+0x1b2/0x450 [kvm] ? hrtimer_try_to_cancel+0x2c/0x120 ? kvm_read_l1_tsc+0x55/0x60 [kvm] try_async_pf+0x66/0x230 [kvm] ? kvm_host_page_size+0x90/0xa0 [kvm] tdp_page_fault+0x130/0x280 [kvm] kvm_mmu_page_fault+0x5f/0xf0 [kvm] handle_ept_violation+0x94/0x180 [kvm_intel] vmx_handle_exit+0x1d3/0x1440 [kvm_intel] ? atomic_switch_perf_msrs+0x6f/0xa0 [kvm_intel] ? vmx_vcpu_run+0x2d1/0x490 [kvm_intel] kvm_arch_vcpu_ioctl_run+0x81d/0x16a0 [kvm] ? wake_up_q+0x44/0x80 kvm_vcpu_ioctl+0x33c/0x620 [kvm] ? __vfs_write+0x37/0x160 do_vfs_ioctl+0xa2/0x5d0 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x1a/0xa4 Cc: <sta...@vger.kernel.org> Cc: Andrew Morton <a...@linux-foundation.org> Fixes: ab68f2622136 ("/dev/dax, pmem: direct access to persistent memory") Reported-by: Abhilash Kumar Mulumudi <m.abhilash-ku...@hpe.com> Reported-by: Toshi Kani <toshi.k...@hpe.com> Tested-by: Toshi Kani <toshi.k...@hpe.com> Signed-off-by: Dan Williams <dan.j.willi...@intel.com> --- drivers/dax/pmem.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c index dfb168568af1..1f01e98c83c7 100644 --- a/drivers/dax/pmem.c +++ b/drivers/dax/pmem.c @@ -116,6 +116,9 @@ static int dax_pmem_probe(struct device *dev) if (rc) return rc; + /* adjust the dax_region resource to the start of data */ + res.start += le64_to_cpu(pfn_sb->dataoff); + nd_region = to_nd_region(dev->parent); dax_region = alloc_dax_region(dev, nd_region->id, &res, le32_to_cpu(pfn_sb->align), addr, PFN_DEV|PFN_MAP);