From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C953B387566 for ; Mon, 4 May 2026 22:42:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777934558; cv=none; b=ZgKXevfg4fenE/6omZZJOVMVHoEbWVSe2e1JD7w+87AKWVuV4Pbiz3o4zTFC5SPz9vx3lTunSqO10wDmcappxpomLR9ZzAucz/QlzJLilUVy2BQ70VC1oFYRWRSOD5IDBU04pJqy9g4TwzyoCjaD7DhWZZ+FdwYzsZbM3XoDe2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777934558; c=relaxed/simple; bh=rDuwAeB4ha58gotrneg8EsaMOT+AwZ1dhESIVBbvmoQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=QeIETYUwicw0H6VVw/YuPt2ECleYJ9nod3zwtJ4hThZa+e4yXzO+XqDsY94UdIVHCsvxTBaxoFPb1Oq1zU1nPPXcOdJjzrNP56fndDBil6oq5sAzFgH+rb4i/ikz43+4w6FXdAuTK+suLCSeSOnxdT07KpuPxNhXlQDcsIQYGEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=CBcINOEG; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CBcINOEG" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-8353b042152so2149118b3a.3 for ; Mon, 04 May 2026 15:42:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1777934556; x=1778539356; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=uWygzttyaDGZ8i1sz2PNqa3rZtIdDV4A7Q8dk96hn1w=; b=CBcINOEGtgq/zjoVaaEJplp+LKCXJsutpTTEfZ7fWHpKaRv96FYaiK/j6JfnlnqHim vYUXw+6KsreOWBl968Bvy1Xhk1tZ6tePc1EwyWJjQ2Ekrn51DNYjmzHdN0idND79pv8X kTdCiO1NL73BpnabSho2mva1+6MANYogNCTqqLcmsdFLdP2XE7DELfKx/QyScPQK6Mt8 fn+sqFaW+X+J5UZecZyDl8y/wdm23XeztHxguX0XuLc3O4I/R0kWqcl9RcHCG7vElaf4 W+NF+TMHnMC1GX0y6/BwpkWUGONdixewRQ6UGKYVnr9aewLEVsGd6XfCSOSEkJREQHGd lagA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777934556; x=1778539356; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=uWygzttyaDGZ8i1sz2PNqa3rZtIdDV4A7Q8dk96hn1w=; b=Th//6HyddJSpbs55cMuAYM7jPwdzZ7+e9+xM0CFgSQ+G6ltX/wICCF3ilwzBvo4gX1 QuSdimxMSBScus1rCymbvSjorqq/GMJ7EJckcQFJF3/KfZzA2t7mLY71+iOrwNwS78PL ic2rS9l7hbcFDt2h0aupZxDzzeo+NmyimeAqAOZONJHWiRO7DQV9IaR79+diNeAksKK4 QlhIgKU54dNgxwmtoRdp7XQEQHq4+wxPxq5nZQgquh/fPNcUDzGtAQokP6XgYWl4/zMt f539coNxfJS6Tr3bKvOdbl0xpz0lQslWNZ27vuUtQQg3KQAGjsViuX03lf8wEuO45cJU EVcA== X-Forwarded-Encrypted: i=1; AFNElJ/0+vQMqWHWwLhMJmyahQfaElSsSZHk1dZLkdIScPwPrGHmunk+0Mz8PugTn5gWlEhRJ9O+tBAY8K7xgEE=@vger.kernel.org X-Gm-Message-State: AOJu0YwqeGPCJf9KZWrR2dcpdsH8I/U/9xKZUvd9fhpgxPa/xGA/kUth CB6x9oOPsLO+D+QH283weqe8e+X7yuD32ZE7GFIwniHY8+RYMcEg6HZyxCM8WABDC4j6FXaMq5C UYJC2iqYc4Ck1yPwlucc/vw== X-Received: from pfbhh11.prod.google.com ([2002:a05:6a00:868b:b0:82f:a959:4a7f]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:181b:b0:823:d2c:b156 with SMTP id d2e1a72fcca58-8352d037329mr12663141b3a.5.1777934555976; Mon, 04 May 2026 15:42:35 -0700 (PDT) Date: Mon, 4 May 2026 22:42:08 +0000 In-Reply-To: <20260504224213.1049426-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260504224213.1049426-1-jthoughton@google.com> X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog Message-ID: <20260504224213.1049426-2-jthoughton@google.com> Subject: [PATCH 1/5] KVM: arm64: Grab KVM MMU write lock in kvm_arch_flush_shadow_all() From: James Houghton To: Paolo Bonzini Cc: Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Sean Christopherson , Gavin Shan , Shaoqin Huang , Ricardo Koller , Tianrui Zhao , Bibo Mao , Huacai Chen , James Hogan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, James Houghton , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" kvm_arch_flush_shadow_all() may sometimes be called on the same `kvm` concurrently in the event that the KVM's `mm` is __mmput() at the same time that last reference to the KVM is being dropped. T1 T2 KVM_CREATE_VM Get VM file from T1 close VM exit_mm() close VM T1: exit_mm() -> kvm_mmu_notifier_release() -> kvm_flush_shadow_all(), with only the KVM srcu read lock held. T2: kvm_vm_release() ---> mmu_notifier_unregister() -> kvm_mmu_notifier_release() -> kvm_flush_shadow_all(), again, with only the KVM srcu read lock held. This leads to a potential double-free of kvm->arch.kvm_mmu_free_memory_cache and now with NV kvm->arch.nested_mmus. Cc: stable@vger.kernel.org Fixes: e7bf7a490c68 ("KVM: arm64: Split huge pages when dirty logging is enabled") Signed-off-by: James Houghton --- arch/arm64/include/asm/kvm_mmu.h | 1 + arch/arm64/kvm/mmu.c | 23 +++++++++++++++++++---- arch/arm64/kvm/nested.c | 4 +++- 3 files changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index 01e9c72d6aa7..30d5c24fcebb 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -178,6 +178,7 @@ void stage2_unmap_vm(struct kvm *kvm); int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long type); void kvm_uninit_stage2_mmu(struct kvm *kvm); void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu); +void kvm_free_stage2_pgd_locked(struct kvm_s2_mmu *mmu); int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa, phys_addr_t pa, unsigned long size, bool writable); diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index d089c107d9b7..4bab407d43bb 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1021,7 +1021,9 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t void kvm_uninit_stage2_mmu(struct kvm *kvm) { - kvm_free_stage2_pgd(&kvm->arch.mmu); + lockdep_assert_held_write(&kvm->mmu_lock); + + kvm_free_stage2_pgd_locked(&kvm->arch.mmu); kvm_mmu_free_memory_cache(&kvm->arch.mmu.split_page_cache); } @@ -1095,12 +1097,14 @@ void stage2_unmap_vm(struct kvm *kvm) srcu_read_unlock(&kvm->srcu, idx); } -void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) +static void __kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu, bool locked) { struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); struct kvm_pgtable *pgt = NULL; - write_lock(&kvm->mmu_lock); + if (!locked) + write_lock(&kvm->mmu_lock); + pgt = mmu->pgt; if (pgt) { mmu->pgd_phys = 0; @@ -1111,7 +1115,8 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) if (kvm_is_nested_s2_mmu(kvm, mmu)) kvm_init_nested_s2_mmu(mmu); - write_unlock(&kvm->mmu_lock); + if (!locked) + write_unlock(&kvm->mmu_lock); if (pgt) { kvm_stage2_destroy(pgt); @@ -1119,6 +1124,16 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) } } +void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) +{ + __kvm_free_stage2_pgd(mmu, false); +} + +void kvm_free_stage2_pgd_locked(struct kvm_s2_mmu *mmu) +{ + __kvm_free_stage2_pgd(mmu, true); +} + static void hyp_mc_free_fn(void *addr, void *mc) { struct kvm_hyp_memcache *memcache = mc; diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 883b6c1008fb..977598bff5e6 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1190,11 +1190,13 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm) { int i; + guard(write_lock)(&kvm->mmu_lock); + for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; if (!WARN_ON(atomic_read(&mmu->refcnt))) - kvm_free_stage2_pgd(mmu); + kvm_free_stage2_pgd_locked(mmu); } kvfree(kvm->arch.nested_mmus); kvm->arch.nested_mmus = NULL; -- 2.54.0.545.g6539524ca2-goog