From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E79D3824A3; Mon, 28 Oct 2024 06:55:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730098505; cv=none; b=KGt9C0u44vSo6lj06gcb5aGaVq15Qfg27Lp4ZLmtiHyEbFqaHVZ5lK89437N+B/V8XhkXfsR4y92NopJFpHFY4XlhQrXM8Ts62EnUx+X5g6vzfVRrGwtc/C39fLoQlCnwGYcu7BPgNowG1pWe7EqtyxrkH19h+2dpq1XdLM/LJA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730098505; c=relaxed/simple; bh=Mf8Nhp9uaGpYl8gGqORVD7crVlA4ceU5wwVE/DSthx4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RPrtGN/d29qcDb8sJyKbtxSzZaVpQXujQQhwnkdAlPI+WL2GIfF/m/qddm4IhPqMG7dFE/S9lPE1tRGUaBG8HoEcUlIHhfT5pBOM5oUVuUBqoJmd2LA8QCYvTpmWCNH8pSCOeBseyXpOpvdbL1Cami6QTFafU3Fa0oN2qEwVzpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OeUlqVQ8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="OeUlqVQ8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 892E1C4CEC3; Mon, 28 Oct 2024 06:55:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730098504; bh=Mf8Nhp9uaGpYl8gGqORVD7crVlA4ceU5wwVE/DSthx4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OeUlqVQ83Qb55k3+kVrLMPzO/021GeDAVCjPmsOnhlzIcq8++6yuOJ6uHGy/ggm0o 49b9Au2yD8/0N1XmNfNrnc3gAw37lx/b219UNKvtEusfBBW1A7bWSXr7FrbW7rk6MX lDsduXGgzDa5WlQ9reEOWxvmiD+5fDvNIfejFg30= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexander Potapenko , Oliver Upton , Marc Zyngier Subject: [PATCH 6.11 219/261] KVM: arm64: Unregister redistributor for failed vCPU creation Date: Mon, 28 Oct 2024 07:26:01 +0100 Message-ID: <20241028062317.594950520@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241028062312.001273460@linuxfoundation.org> References: <20241028062312.001273460@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oliver Upton commit ae8f8b37610269009326f4318df161206c59843e upstream. Alex reports that syzkaller has managed to trigger a use-after-free when tearing down a VM: BUG: KASAN: slab-use-after-free in kvm_put_kvm+0x300/0xe68 virt/kvm/kvm_main.c:5769 Read of size 8 at addr ffffff801c6890d0 by task syz.3.2219/10758 CPU: 3 UID: 0 PID: 10758 Comm: syz.3.2219 Not tainted 6.11.0-rc6-dirty #64 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x17c/0x1a8 arch/arm64/kernel/stacktrace.c:317 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324 __dump_stack lib/dump_stack.c:93 [inline] dump_stack_lvl+0x94/0xc0 lib/dump_stack.c:119 print_report+0x144/0x7a4 mm/kasan/report.c:377 kasan_report+0xcc/0x128 mm/kasan/report.c:601 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381 kvm_put_kvm+0x300/0xe68 virt/kvm/kvm_main.c:5769 kvm_vm_release+0x4c/0x60 virt/kvm/kvm_main.c:1409 __fput+0x198/0x71c fs/file_table.c:422 ____fput+0x20/0x30 fs/file_table.c:450 task_work_run+0x1cc/0x23c kernel/task_work.c:228 do_notify_resume+0x144/0x1a0 include/linux/resume_user_mode.h:50 el0_svc+0x64/0x68 arch/arm64/kernel/entry-common.c:169 el0t_64_sync_handler+0x90/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 Upon closer inspection, it appears that we do not properly tear down the MMIO registration for a vCPU that fails creation late in the game, e.g. a vCPU w/ the same ID already exists in the VM. It is important to consider the context of commit that introduced this bug by moving the unregistration out of __kvm_vgic_vcpu_destroy(). That change correctly sought to avoid an srcu v. config_lock inversion by breaking up the vCPU teardown into two parts, one guarded by the config_lock. Fix the use-after-free while avoiding lock inversion by adding a special-cased unregistration to __kvm_vgic_vcpu_destroy(). This is safe because failed vCPUs are torn down outside of the config_lock. Cc: stable@vger.kernel.org Fixes: f616506754d3 ("KVM: arm64: vgic: Don't hold config_lock while unregistering redistributors") Reported-by: Alexander Potapenko Signed-off-by: Oliver Upton Link: https://lore.kernel.org/r/20241007223909.2157336-1-oliver.upton@linux.dev Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kvm/vgic/vgic-init.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index e7c53e8af3d1..57aedf7b2b76 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -417,8 +417,28 @@ static void __kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu) kfree(vgic_cpu->private_irqs); vgic_cpu->private_irqs = NULL; - if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) + if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) { + /* + * If this vCPU is being destroyed because of a failed creation + * then unregister the redistributor to avoid leaving behind a + * dangling pointer to the vCPU struct. + * + * vCPUs that have been successfully created (i.e. added to + * kvm->vcpu_array) get unregistered in kvm_vgic_destroy(), as + * this function gets called while holding kvm->arch.config_lock + * in the VM teardown path and would otherwise introduce a lock + * inversion w.r.t. kvm->srcu. + * + * vCPUs that failed creation are torn down outside of the + * kvm->arch.config_lock and do not get unregistered in + * kvm_vgic_destroy(), meaning it is both safe and necessary to + * do so here. + */ + if (kvm_get_vcpu_by_id(vcpu->kvm, vcpu->vcpu_id) != vcpu) + vgic_unregister_redist_iodev(vcpu); + vgic_cpu->rd_iodev.base_addr = VGIC_ADDR_UNDEF; + } } void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu) -- 2.47.0