dax: fix device-dax region base

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: 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]
   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]
   kvm_arch_vcpu_ioctl_run+0x81d/0x16a0 [kvm]
   kvm_vcpu_ioctl+0x33c/0x620 [kvm]
   do_vfs_ioctl+0xa2/0x5d0
   SyS_ioctl+0x79/0x90
   entry_SYSCALL_64_fastpath+0x1a/0xa4

Fixes: ab68f2622136 ("/dev/dax, pmem: direct access to persistent memory")
Link: http://lkml.kernel.org/r/147205536732.1606.8994275381938837346.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Abhilash Kumar Mulumudi <m.abhilash-kumar@hpe.com>
Reported-by: Toshi Kani <toshi.kani@hpe.com>
Tested-by: Toshi Kani <toshi.kani@hpe.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index dfb168568af1a6d2ba163a7010d611ec0ad3a3f0..1f01e98c83c7ddcccecd50e11671e3b519b2c136 100644 (file)
--- 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);