4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrea Arcangeli <aarca...@redhat.com>

commit e8fd5e9e9984675f45b9a5485909c143fbde248f upstream.

memslot->userfault_addr is set by the kernel with a mmap executed
from the kernel but the userland can still munmap it and lead to the
below oops after memslot->userfault_addr points to a host virtual
address that has no vma or mapping.

[  327.538306] BUG: unable to handle kernel paging request at fffffffffffffffe
[  327.538407] IP: [<ffffffff811a7b55>] put_page+0x5/0x50
[  327.538474] PGD 1a01067 PUD 1a03067 PMD 0
[  327.538529] Oops: 0000 [#1] SMP
[  327.538574] Modules linked in: macvtap macvlan xt_CHECKSUM iptable_mangle 
ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat 
nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT 
iptable_filter ip_tables tun bridge stp llc rpcsec_gss_krb5 nfsv4 dns_resolver 
nfs fscache xprtrdma ib_isert iscsi_target_mod ib_iser libiscsi 
scsi_transport_iscsi ib_srpt target_core_mod ib_srp scsi_transport_srp scsi_tgt 
ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm ib_cm iw_cm ipmi_devintf 
iTCO_wdt iTCO_vendor_support intel_powerclamp coretemp dcdbas intel_rapl 
kvm_intel kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel lrw 
gf128mul glue_helper ablk_helper cryptd pcspkr sb_edac edac_core ipmi_si 
ipmi_msghandler acpi_pad wmi acpi_power_meter lpc_ich mfd_core mei_me
[  327.539488]  mei shpchp nfsd auth_rpcgss nfs_acl lockd grace sunrpc mlx4_ib 
ib_sa ib_mad ib_core mlx4_en vxlan ib_addr ip_tunnel xfs libcrc32c sd_mod 
crc_t10dif crct10dif_common crc32c_intel mgag200 syscopyarea sysfillrect 
sysimgblt i2c_algo_bit drm_kms_helper ttm drm ahci i2c_core libahci mlx4_core 
libata tg3 ptp pps_core megaraid_sas ntb dm_mirror dm_region_hash dm_log dm_mod
[  327.539956] CPU: 3 PID: 3161 Comm: qemu-kvm Not tainted 
3.10.0-240.el7.userfault19.4ca4011.x86_64.debug #1
[  327.540045] Hardware name: Dell Inc. PowerEdge R420/0CN7CM, BIOS 2.1.2 
01/20/2014
[  327.540115] task: ffff8803280ccf00 ti: ffff880317c58000 task.ti: 
ffff880317c58000
[  327.540184] RIP: 0010:[<ffffffff811a7b55>]  [<ffffffff811a7b55>] 
put_page+0x5/0x50
[  327.540261] RSP: 0018:ffff880317c5bcf8  EFLAGS: 00010246
[  327.540313] RAX: 00057ffffffff000 RBX: ffff880616a20000 RCX: 0000000000000000
[  327.540379] RDX: 0000000000002014 RSI: 00057ffffffff000 RDI: fffffffffffffffe
[  327.540445] RBP: ffff880317c5bd10 R08: 0000000000000103 R09: 0000000000000000
[  327.540511] R10: 0000000000000000 R11: 0000000000000000 R12: fffffffffffffffe
[  327.540576] R13: 0000000000000000 R14: ffff880317c5bd70 R15: ffff880317c5bd50
[  327.540643] FS:  00007fd230b7f700(0000) GS:ffff880630800000(0000) 
knlGS:0000000000000000
[  327.540717] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  327.540771] CR2: fffffffffffffffe CR3: 000000062a2c3000 CR4: 00000000000427e0
[  327.540837] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  327.540904] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  327.540974] Stack:
[  327.541008]  ffffffffa05d6d0c ffff880616a20000 0000000000000000 
ffff880317c5bdc0
[  327.541093]  ffffffffa05ddaa2 0000000000000000 00000000002191bf 
00000042f3feab2d
[  327.541177]  00000042f3feab2d 0000000000000002 0000000000000001 
0321000000000000
[  327.541261] Call Trace:
[  327.541321]  [<ffffffffa05d6d0c>] ? 
kvm_vcpu_reload_apic_access_page+0x6c/0x80 [kvm]
[  327.543615]  [<ffffffffa05ddaa2>] vcpu_enter_guest+0x3f2/0x10f0 [kvm]
[  327.545918]  [<ffffffffa05e2f10>] kvm_arch_vcpu_ioctl_run+0x2b0/0x5a0 [kvm]
[  327.548211]  [<ffffffffa05e2d02>] ? kvm_arch_vcpu_ioctl_run+0xa2/0x5a0 [kvm]
[  327.550500]  [<ffffffffa05ca845>] kvm_vcpu_ioctl+0x2b5/0x680 [kvm]
[  327.552768]  [<ffffffff810b8d12>] ? creds_are_invalid.part.1+0x12/0x50
[  327.555069]  [<ffffffff810b8d71>] ? creds_are_invalid+0x21/0x30
[  327.557373]  [<ffffffff812d6066>] ? 
inode_has_perm.isra.49.constprop.65+0x26/0x80
[  327.559663]  [<ffffffff8122d985>] do_vfs_ioctl+0x305/0x530
[  327.561917]  [<ffffffff8122dc51>] SyS_ioctl+0xa1/0xc0
[  327.564185]  [<ffffffff816de829>] system_call_fastpath+0x16/0x1b
[  327.566480] Code: 0b 31 f6 4c 89 e7 e8 4b 7f ff ff 0f 0b e8 24 fd ff ff e9 
a9 fd ff ff 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90 <48> f7 
07 00 c0 00 00 55 48 89 e5 75 2a 8b 47 1c 85 c0 74 1e f0

Signed-off-by: Andrea Arcangeli <aarca...@redhat.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/x86/kvm/x86.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6141,6 +6141,8 @@ void kvm_vcpu_reload_apic_access_page(st
                return;
 
        page = gfn_to_page(vcpu->kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
+       if (is_error_page(page))
+               return;
        kvm_x86_ops->set_apic_access_page_addr(vcpu, page_to_phys(page));
 
        /*


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