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bh=xvqyLpPA5kcKjuswGO1+kIpP11dfUKZHmvVJw9JK1n0=; b=hu+n6ol+k6zixjg+FuFSGnJCFD+d+2kDX/taVXsJAd+UsgD8ArHZy/REKpcJ9+tBWc k9CbMRYyhLuiA/ACKhmIrUVuElC1qoXvNpCDj7R8RogdZnN81DNUkcmyPr+Msv+sixjj RjM0B7SwauhCnRuYZFwpZm1rPb/QbF/TYvitZJjeYvIvBnxwFn03I6KSJHB90MvSJxAO hjIVj/fZs5092vKULMTwaaOLULBjjN4uf4MywtLoxkWX9SKpB77nWXBok81BNlhNPIy6 9LzYnmYByZIDwnb4yKSDbZ8MNPRqvxUZewmQlapEEdXoAfZXeYniGEVAcwjJvyOKw41j vYhA== X-Gm-Message-State: APjAAAX/SZiO/MSpZ5FmevKQs4FWdpbh4F+VV8h/wMrtANWxUXi5L0ja m3FDjVXW/PxfS0DEzlYvWMq8qt4v8OyXlzpaXoBq+w== X-Google-Smtp-Source: APXvYqxUYk11cnSmSgrLa6DZPJ/i1J3bR4EJC27ZaxQ5lVBCQUv8ymCjuBB6qkW8ExbmrxZTlQ/AFYCxW/muga/juks= X-Received: by 2002:a5d:8d8f:: with SMTP id b15mr16562550ioj.296.1573584558733; Tue, 12 Nov 2019 10:49:18 -0800 (PST) MIME-Version: 1.0 References: <1573478741-30959-1-git-send-email-pbonzini@redhat.com> <1573478741-30959-2-git-send-email-pbonzini@redhat.com> In-Reply-To: <1573478741-30959-2-git-send-email-pbonzini@redhat.com> From: Jim Mattson Date: Tue, 12 Nov 2019 10:49:07 -0800 Message-ID: Subject: Re: [PATCH 1/2] KVM: Fix NULL-ptr deref after kvm_create_vm fails To: Paolo Bonzini Cc: LKML , kvm list , Wanpeng Li , Junaid Shahid Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 11, 2019 at 5:25 AM Paolo Bonzini wrote: > > 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 deferenced 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. Thanks for doing this! > 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 > Cc: Wanpeng Li > Signed-off-by: Paolo Bonzini > --- > virt/kvm/kvm_main.c | 18 +++++++++--------- > 1 file 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); Nit: I would keep the BUILD_BUG_ON closer to the memslot allocation. > + 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 @@ static struct kvm *kvm_create_vm(unsigned long type) > 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); > -- > 1.8.3.1 Reviewed-by: Jim Mattson