Re: KVM: fix cleanup_srcu_struct use-after-free

[Jan Kiszka <jan.kiszka@siemens.com>]

Marcelo Tosatti wrote:
> kvm_destroy_vm should free "struct kvm" after cleanup_srcu_struct.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e0a591d..c828a39 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -509,8 +509,8 @@ static void kvm_destroy_vm(struct kvm *kvm)
>  #else
>  	kvm_arch_flush_shadow(kvm);
>  #endif
> -	kvm_arch_destroy_vm(kvm);
>  	cleanup_srcu_struct(&kvm->srcu);
> +	kvm_arch_destroy_vm(kvm);
>  	hardware_disable_all();
>  	mmdrop(mm);
>  }

This should be responsible for

BUG: unable to handle kernel paging request at ffffffffffffffff
IP: [<ffffffff802533d2>] srcu_read_lock+0x16/0x21
PGD 203067 PUD 204067 PMD 0
Oops: 0000 [1] SMP
last sysfs file: /sys/devices/virtual/backlight/acpi_video0/brightness
CPU 0
Modules linked in: kvm_intel(N) kvm(N) ip6t_LOG xt_pkttype xt_TCPMSS xt_tcpudp ipt_LOG xt_limit iptable_nat nf_nat xt_physdev coretemp(N) sco bridge stp rfcomm bnep l2cap snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device i915 drm af_packet ip6t_REJECT nf_conntrack_ipv6 ip6table_raw xt_NOTRACK ipt_REJECT xt_state iptable_raw iptable_filter ip6table_mangle nf_conntrack_netbios_ns nf_conntrack_ipv4 nf_conntrack ip_tables cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq ip6table_filter ip6_tables x_tables ipv6 microcode fuse ohci_hcd loop arc4 ecb o2scr(N) ath5k(N) mac80211(N) led_class snd_hda_intel pcmcia ath(N) snd_pcm snd_timer snd_page_alloc snd_hwdep yenta_socket sdhci_pci rtc_cmos btusb rsrc_nonstatic iTCO_wdt i2c_i801 sdhci rtc_core cfg80211(N) video ppdev snd iTCO_
 vendor_support ohci1394 pcmcia_core fujitsu_laptop output button pcspkr rfkill_backport(N) mmc_core ac battery joydev rtc_lib serio_raw bluetooth i2c_core soundcore parport_pc ieee1394 sky2 
parport intel_agp sg sha256_generic aes_x86_64 aes_generic cbc dm_crypt crypto_blkcipher usbhid hid ff_memless uhci_hcd sd_mod crc_t10dif ehci_hcd usbcore dm_snapshot dm_mod edd ext3 mbcache jbd fan ata_piix ahci libata scsi_mod dock thermal processor thermal_sys hwmon [last unloaded: kvm]
Supported: No
Pid: 13994, comm: qemu-system-x86 Tainted: G        W 2.6.27.42-0.1-default #1
RIP: 0010:[<ffffffff802533d2>]  [<ffffffff802533d2>] srcu_read_lock+0x16/0x21
RSP: 0018:ffff88001e169ca0  EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff88004eacc040 RCX: 0000000000000000
RDX: ffffffffffffffff RSI: 0000000000000003 RDI: ffff88005b3e8030
RBP: 0000000000000000 R08: 0000000000000200 R09: ffff880001101600
R10: 0000000000000002 R11: ffffffffa0569efe R12: ffff88005b3e8008
R13: ffff88005b3e8010 R14: ffff88005b3e8000 R15: 0000000000000000
FS:  00007f47680bf950(0000) GS:ffffffff80a43080(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffffffffffffffff CR3: 000000001c53c000 CR4: 00000000000026e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process qemu-system-x86 (pid: 13994, threadinfo ffff88001e168000, task ffff8800439d61c0)
Stack:  ffffffffa05354c4 0000000000000000 ffff88004eacc040 ffff88005b3e8008
 ffffffffa05339c6 ffff88004eacc040 ffffffffa0569f7d ffff88005b3e8000
 ffffffffa05357b5 ffff88005b3e8000 0000000000000003 ffff8800214e2180
Call Trace:
 [<ffffffffa05354c4>] kvm_arch_vcpu_uninit+0x1b/0x48 [kvm]
 [<ffffffffa05339c6>] kvm_vcpu_uninit+0x9/0x15 [kvm]
 [<ffffffffa0569f7d>] vmx_free_vcpu+0x7f/0x8f [kvm_intel]
 [<ffffffffa05357b5>] kvm_arch_destroy_vm+0x78/0x111 [kvm]
 [<ffffffffa053315b>] kvm_put_kvm+0xd4/0xfe [kvm]
 [<ffffffffa0533951>] kvm_vcpu_release+0x13/0x17 [kvm]
 [<ffffffff802b27e8>] __fput+0xa1/0x165
 [<ffffffff802afef1>] filp_close+0x5b/0x62
 [<ffffffff8023f4b9>] put_files_struct+0x64/0xc2
 [<ffffffff80241005>] do_exit+0x226/0x325
 [<ffffffff8024116b>] do_group_exit+0x67/0x94
 [<ffffffff80249d45>] get_signal_to_deliver+0x2f4/0x313
 [<ffffffff8020b980>] do_signal+0x62/0x171
 [<ffffffff8020babe>] do_notify_resume+0x2f/0x50
 [<ffffffff8020c367>] ptregscall_common+0x67/0xb0
 [<ffffffff8020c082>] sysret_signal+0x1a/0x25
 [<00007f477f542fdd>] 0x7f477f542fdd


Code: ef e8 6f fc ff ff eb 02 31 db 5e 89 d8 5b 5d 41 5c 41 5d c3 90 8b 07 83 e0 01 48 8b 57 08 65 8b 0c 25 24 00 00 00 89 c9 48 f7 d2 <48> 8b 0c ca 48 63 d0 ff 04 91 c3 48 8b 47 08 48 63 f6 65 8b 14
RIP  [<ffffffff802533d2>] srcu_read_lock+0x16/0x21
 RSP <ffff88001e169ca0>
CR2: ffffffffffffffff
---[ end trace bf4e203c69d904ec ]---

Ie. we first release the srcu struct in kvm_destroy_vm but then try to
acquire the lock again in kvm_arch_vcpu_uninit.

Jan

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