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authorPaolo Bonzini <pbonzini@redhat.com>2019-11-04 12:16:49 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2019-11-11 15:48:02 +0100
commit8a44119a98bee4381d28f3ed1e41dfacf5c3aa6d (patch)
treeeec75833928c025e33e877d0b2d50d27230d14e5 /virt
parent31f4f5b495a62c9a8b15b1c3581acd5efeb9af8c (diff)
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KVM: Fix NULL-ptr deref after kvm_create_vm fails
Reported by syzkaller: kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 14727 Comm: syz-executor.3 Not tainted 5.4.0-rc4+ #0 RIP: 0010:kvm_coalesced_mmio_init+0x5d/0x110 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:121 Call Trace: kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3446 [inline] kvm_dev_ioctl+0x781/0x1490 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3494 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x196/0x1150 fs/ioctl.c:696 ksys_ioctl+0x62/0x90 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Commit 9121923c457d ("kvm: Allocate memslots and buses before calling kvm_arch_init_vm") moves memslots and buses allocations around, however, if kvm->srcu/irq_srcu fails initialization, NULL will be returned instead of error code, NULL will not be intercepted in kvm_dev_ioctl_create_vm() and be dereferenced by kvm_coalesced_mmio_init(), this patch fixes it. Moving the initialization is required anyway to avoid an incorrect synchronize_srcu that was also reported by syzkaller: wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136 __synchronize_srcu+0x197/0x250 kernel/rcu/srcutree.c:921 synchronize_srcu_expedited kernel/rcu/srcutree.c:946 [inline] synchronize_srcu+0x239/0x3e8 kernel/rcu/srcutree.c:997 kvm_page_track_unregister_notifier+0xe7/0x130 arch/x86/kvm/page_track.c:212 kvm_mmu_uninit_vm+0x1e/0x30 arch/x86/kvm/mmu.c:5828 kvm_arch_destroy_vm+0x4a2/0x5f0 arch/x86/kvm/x86.c:9579 kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:702 [inline] so do it. Reported-by: syzbot+89a8060879fa0bd2db4f@syzkaller.appspotmail.com Reported-by: syzbot+e27e7027eb2b80e44225@syzkaller.appspotmail.com Fixes: 9121923c457d ("kvm: Allocate memslots and buses before calling kvm_arch_init_vm") Cc: Jim Mattson <jmattson@google.com> Cc: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d6f0696d98ef..e22ff63e5b1a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -645,6 +645,11 @@ static struct kvm *kvm_create_vm(unsigned long type)
BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);
+ if (init_srcu_struct(&kvm->srcu))
+ goto out_err_no_srcu;
+ if (init_srcu_struct(&kvm->irq_srcu))
+ goto out_err_no_irq_srcu;
+
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
struct kvm_memslots *slots = kvm_alloc_memslots();
@@ -675,11 +680,6 @@ static struct kvm *kvm_create_vm(unsigned long type)
INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif
- if (init_srcu_struct(&kvm->srcu))
- goto out_err_no_srcu;
- if (init_srcu_struct(&kvm->irq_srcu))
- goto out_err_no_irq_srcu;
-
r = kvm_init_mmu_notifier(kvm);
if (r)
goto out_err;
@@ -693,10 +693,6 @@ static struct kvm *kvm_create_vm(unsigned long type)
return kvm;
out_err:
- cleanup_srcu_struct(&kvm->irq_srcu);
-out_err_no_irq_srcu:
- cleanup_srcu_struct(&kvm->srcu);
-out_err_no_srcu:
hardware_disable_all();
out_err_no_disable:
kvm_arch_destroy_vm(kvm);
@@ -706,6 +702,10 @@ out_err_no_arch_destroy_vm:
kfree(kvm_get_bus(kvm, i));
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
+ cleanup_srcu_struct(&kvm->irq_srcu);
+out_err_no_irq_srcu:
+ cleanup_srcu_struct(&kvm->srcu);
+out_err_no_srcu:
kvm_arch_free_vm(kvm);
mmdrop(current->mm);
return ERR_PTR(r);