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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-Transfer-Encoding: quoted-printable 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 en= abled") 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); =20 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_s= 2_mmu *mmu, unsigned long t =20 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); } =20 @@ -1095,12 +1097,14 @@ void stage2_unmap_vm(struct kvm *kvm) srcu_read_unlock(&kvm->srcu, idx); } =20 -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 =3D kvm_s2_mmu_to_kvm(mmu); struct kvm_pgtable *pgt =3D NULL; =20 - write_lock(&kvm->mmu_lock); + if (!locked) + write_lock(&kvm->mmu_lock); + pgt =3D mmu->pgt; if (pgt) { mmu->pgd_phys =3D 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); =20 - write_unlock(&kvm->mmu_lock); + if (!locked) + write_unlock(&kvm->mmu_lock); =20 if (pgt) { kvm_stage2_destroy(pgt); @@ -1119,6 +1124,16 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) } } =20 +void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) +{ + __kvm_free_stage2_pgd(mmu, false); 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Mon, 04 May 2026 15:42:38 -0700 (PDT) Date: Mon, 4 May 2026 22:42:09 +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: <20260504224213.1049426-3-jthoughton@google.com> Subject: [PATCH 2/5] KVM: loongarch: Grab MMU 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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" kvm_arch_flush_shadow_all() may be called concurrently on the same `kvm`. This could at least result in accounting mistakes (e.g. underflows on `kvm->stat.*pages`). Cc: stable@vger.kernel.org Fixes: 752e2cd7b4fb ("LoongArch: KVM: Implement kvm mmu operations") Signed-off-by: James Houghton Reviewed-by: Bibo Mao --- Note: This is compile-tested only! arch/loongarch/kvm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c index a7fa458e3360..5dbce9b18e1c 100644 --- a/arch/loongarch/kvm/mmu.c +++ b/arch/loongarch/kvm/mmu.c @@ -486,7 +486,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, =20 void kvm_arch_flush_shadow_all(struct kvm *kvm) { - kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 0); + kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 1); } =20 void kvm_arch_flush_shadow_memslot(struct kvm *kvm, struct kvm_memory_slot= *slot) --=20 2.54.0.545.g6539524ca2-goog From nobody Sun Jun 14 01:34:30 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 41BC338A73F for ; 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Mon, 04 May 2026 15:42:41 -0700 (PDT) Date: Mon, 4 May 2026 22:42:10 +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: <20260504224213.1049426-4-jthoughton@google.com> Subject: [PATCH 3/5] KVM: mips: Grab MMU 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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" kvm_mips_flush_gpa_pt() expects the MMU lock to be held; it is not in this path. This can lead to a double-free of page table entries if kvm_arch_flush_shadow_all() is called twice on the same `kvm` concurrently; such a scenario is possible. Cc: stable@vger.kernel.org Fixes: b62091108633 ("KVM: MIPS: Implement kvm_arch_flush_shadow_all/memslo= t") Signed-off-by: James Houghton --- Note: This is compile-tested only! arch/mips/kvm/mips.c | 2 ++ arch/mips/kvm/mmu.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index a53abbba43ea..463b6c4aa62c 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -180,6 +180,8 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int= ioctl, =20 void kvm_arch_flush_shadow_all(struct kvm *kvm) { + guard(spinlock)(&kvm->mmu_lock); + /* Flush whole GPA */ kvm_mips_flush_gpa_pt(kvm, 0, ~0); kvm_flush_remote_tlbs(kvm); diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c index d2c3b6b41f18..5045833f8116 100644 --- a/arch/mips/kvm/mmu.c +++ b/arch/mips/kvm/mmu.c @@ -269,6 +269,8 @@ static bool kvm_mips_flush_gpa_pgd(pgd_t *pgd, unsigned= long start_gpa, */ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn) { + lockdep_assert_held(&kvm->mmu_lock); 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charset="utf-8" All architectures that non-trivially implement this function grab the KVM MMU lock exclusively to prevent things like double-freeing of page table entries and caches. Do so generically to somewhat simplify the architecture-specific logic. Without this change, it is possible for kvm_arch_flush_shadow_all() to be called on the same `kvm` at the same time: if the `kvm`'s mm is destroyed (exit_mm()) at the same time to the final reference to the `kvm` is dropped. Signed-off-by: James Houghton --- arch/arm64/kvm/nested.c | 2 +- arch/loongarch/kvm/mmu.c | 4 +++- arch/mips/kvm/mips.c | 2 +- arch/riscv/kvm/mmu.c | 4 ++-- arch/riscv/kvm/vm.c | 2 ++ arch/x86/kvm/mmu/mmu.c | 4 +--- virt/kvm/kvm_main.c | 3 +++ 7 files changed, 13 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 977598bff5e6..ba2e6c98bd45 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1190,7 +1190,7 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm) { int i; =20 - guard(write_lock)(&kvm->mmu_lock); + lockdep_assert_held_write(&kvm->mmu_lock); =20 for (i =3D 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu =3D &kvm->arch.nested_mmus[i]; diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c index 5dbce9b18e1c..120001da26e4 100644 --- a/arch/loongarch/kvm/mmu.c +++ b/arch/loongarch/kvm/mmu.c @@ -486,7 +486,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, =20 void kvm_arch_flush_shadow_all(struct kvm *kvm) { - kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 1); + lockdep_assert_held(&kvm->mmu_lock); + + kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 0); } =20 void kvm_arch_flush_shadow_memslot(struct kvm *kvm, struct kvm_memory_slot= *slot) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 463b6c4aa62c..4ad9e21a3321 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -180,7 +180,7 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int= ioctl, =20 void kvm_arch_flush_shadow_all(struct kvm *kvm) { - guard(spinlock)(&kvm->mmu_lock); + lockdep_assert_held(&kvm->mmu_lock); =20 /* Flush whole GPA */ kvm_mips_flush_gpa_pt(kvm, 0, ~0); diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c index 2d3def024270..c1b9333f17eb 100644 --- a/arch/riscv/kvm/mmu.c +++ b/arch/riscv/kvm/mmu.c @@ -558,7 +558,8 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm) struct kvm_gstage gstage; void *pgd =3D NULL; =20 - spin_lock(&kvm->mmu_lock); + lockdep_assert_held(&kvm->mmu_lock); + if (kvm->arch.pgd) { kvm_riscv_gstage_init(&gstage, kvm); kvm_riscv_gstage_unmap_range(&gstage, 0UL, @@ -568,7 +569,6 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm) kvm->arch.pgd_phys =3D 0; kvm->arch.pgd_levels =3D 0; } - spin_unlock(&kvm->mmu_lock); =20 if (pgd) free_pages((unsigned long)pgd, get_order(kvm_riscv_gstage_pgd_size)); diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c index a9f083feeb76..f704a64bfc48 100644 --- a/arch/riscv/kvm/vm.c +++ b/arch/riscv/kvm/vm.c @@ -38,7 +38,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) =20 r =3D kvm_riscv_gstage_vmid_init(kvm); if (r) { + spin_lock(&kvm->mmu_lock); kvm_riscv_mmu_free_pgd(kvm); + spin_unlock(&kvm->mmu_lock); return r; } =20 diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 892246204435..6e6f94046b3f 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7352,7 +7352,7 @@ static void kvm_mmu_zap_all(struct kvm *kvm) LIST_HEAD(invalid_list); int ign; =20 - write_lock(&kvm->mmu_lock); + lockdep_assert_held_write(&kvm->mmu_lock); restart: list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) { if (WARN_ON_ONCE(sp->role.invalid)) @@ -7367,8 +7367,6 @@ static void kvm_mmu_zap_all(struct kvm *kvm) =20 if (tdp_mmu_enabled) kvm_tdp_mmu_zap_all(kvm); - - write_unlock(&kvm->mmu_lock); } =20 void kvm_arch_flush_shadow_all(struct kvm *kvm) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 89489996fbc1..f5affd3bfda8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -340,7 +340,10 @@ void kvm_flush_remote_tlbs_memslot(struct kvm *kvm, =20 static void kvm_flush_shadow_all(struct kvm *kvm) { + KVM_MMU_LOCK(kvm); kvm_arch_flush_shadow_all(kvm); + KVM_MMU_UNLOCK(kvm); + kvm_arch_guest_memory_reclaimed(kvm); } =20 --=20 2.54.0.545.g6539524ca2-goog From nobody Sun Jun 14 01:34:30 2026 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (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 1E169387581 for ; Mon, 4 May 2026 22:42:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; 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Mon, 04 May 2026 15:42:54 -0700 (PDT) Date: Mon, 4 May 2026 22:42:12 +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: <20260504224213.1049426-6-jthoughton@google.com> Subject: [PATCH 5/5] DO NOT MERGE: KVM: selftests: Reproducer for arm64 double-free 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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a delay and a counter for the split_page_cache double-free to reliably demonstrate the race. Please see the cover letter and the arm64 fix patch for more information. The selftest is partially written by Gemini. Assisted-by: Gemini:gemini-3-flash-preview Not-signed-off-by: James Houghton --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/mmu.c | 16 +++ tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/transfer_fd_test.c | 129 ++++++++++++++++++ 4 files changed, 147 insertions(+) create mode 100644 tools/testing/selftests/kvm/transfer_fd_test.c diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index 65eead8362e0..5072fc2e2eb8 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -192,6 +192,7 @@ struct kvm_s2_mmu { * Protected by kvm->slots_lock. */ struct kvm_mmu_memory_cache split_page_cache; + int is_freeing; uint64_t split_page_chunk_size; =20 struct kvm_arch *arch; diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 4bab407d43bb..fa05900a5124 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1004,6 +1004,8 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s= 2_mmu *mmu, unsigned long t mmu->split_page_chunk_size =3D KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT; mmu->split_page_cache.gfp_zero =3D __GFP_ZERO; =20 + mmu->is_freeing =3D 0; + mmu->pgd_phys =3D __pa(pgt->pgd); =20 if (kvm_is_nested_s2_mmu(kvm, mmu)) @@ -1021,10 +1023,24 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm= _s2_mmu *mmu, unsigned long t =20 void kvm_uninit_stage2_mmu(struct kvm *kvm) { + int is_freeing; + ktime_t s; + lockdep_assert_held_write(&kvm->mmu_lock); =20 kvm_free_stage2_pgd_locked(&kvm->arch.mmu); + + is_freeing =3D ++kvm->arch.mmu.is_freeing; + s =3D ktime_get(); + + /* Sleep for 10ms */ + while (ktime_to_ns(ktime_get()) - ktime_to_ns(s) < 1E7) {} + + WARN(is_freeing > 1, "detected double-free of split page cache"); + kvm_mmu_free_memory_cache(&kvm->arch.mmu.split_page_cache); + + kvm->arch.mmu.is_freeing--; } =20 static void stage2_unmap_memslot(struct kvm *kvm, diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selft= ests/kvm/Makefile.kvm index 9118a5a51b89..53a1b9c7bff8 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -66,6 +66,7 @@ TEST_GEN_PROGS_COMMON +=3D kvm_page_table_test TEST_GEN_PROGS_COMMON +=3D set_memory_region_test TEST_GEN_PROGS_COMMON +=3D memslot_modification_stress_test TEST_GEN_PROGS_COMMON +=3D memslot_perf_test +TEST_GEN_PROGS_COMMON +=3D transfer_fd_test =20 # Compiled test targets TEST_GEN_PROGS_x86 =3D $(TEST_GEN_PROGS_COMMON) diff --git a/tools/testing/selftests/kvm/transfer_fd_test.c b/tools/testing= /selftests/kvm/transfer_fd_test.c new file mode 100644 index 000000000000..ff2adff9954b --- /dev/null +++ b/tools/testing/selftests/kvm/transfer_fd_test.c @@ -0,0 +1,129 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Test VM file descriptor transfer via Unix Domain Sockets. + */ +#include +#include +#include +#include +#include + +#include "test_util.h" +#include "kvm_util.h" + +static void send_fd(int sock, int fd) +{ + struct msghdr msg =3D {0}; + struct cmsghdr *cmsg; + char buf[CMSG_SPACE(sizeof(int))]; + struct iovec io =3D { + .iov_base =3D "a", + .iov_len =3D 1, + }; + + msg.msg_iov =3D &io; + msg.msg_iovlen =3D 1; + msg.msg_control =3D buf; + msg.msg_controllen =3D sizeof(buf); + + cmsg =3D CMSG_FIRSTHDR(&msg); + cmsg->cmsg_level =3D SOL_SOCKET; + cmsg->cmsg_type =3D SCM_RIGHTS; + cmsg->cmsg_len =3D CMSG_LEN(sizeof(int)); + + *((int *)CMSG_DATA(cmsg)) =3D fd; + + TEST_ASSERT(sendmsg(sock, &msg, 0) =3D=3D 1, "sendmsg failed, errno: %d",= errno); +} + +static int recv_fd(int sock) +{ + struct msghdr msg =3D {0}; + struct cmsghdr *cmsg; + char buf[CMSG_SPACE(sizeof(int))]; + char dummy; + struct iovec io =3D { + .iov_base =3D &dummy, + .iov_len =3D 1, + }; + int fd; + + msg.msg_iov =3D &io; + msg.msg_iovlen =3D 1; + msg.msg_control =3D buf; + msg.msg_controllen =3D sizeof(buf); + + TEST_ASSERT(recvmsg(sock, &msg, 0) =3D=3D 1, "recvmsg failed, errno: %d",= errno); + + cmsg =3D CMSG_FIRSTHDR(&msg); + TEST_ASSERT(cmsg && cmsg->cmsg_level =3D=3D SOL_SOCKET && + cmsg->cmsg_type =3D=3D SCM_RIGHTS, "No FD received"); + + fd =3D *((int *)CMSG_DATA(cmsg)); + return fd; +} + +int main(int argc, char **argv) +{ + pthread_barrierattr_t attr; + pthread_barrier_t *barrier; + int socks[2]; + pid_t pid; + int ret; + + barrier =3D mmap(NULL, sizeof(*barrier), PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1, 0); + TEST_ASSERT(barrier !=3D MAP_FAILED, "mmap failed, errno: %d", errno); + + ret =3D pthread_barrierattr_init(&attr); + TEST_ASSERT(!ret, "pthread_barrierattr_init failed, ret: %d", ret); + + ret =3D pthread_barrierattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); + TEST_ASSERT(!ret, "pthread_barrierattr_setpshared failed, ret: %d", ret); + + ret =3D pthread_barrier_init(barrier, &attr, 2); + TEST_ASSERT(!ret, "pthread_barrier_init failed, ret: %d", ret); + + ret =3D socketpair(AF_UNIX, SOCK_STREAM, 0, socks); + TEST_ASSERT(ret =3D=3D 0, "socketpair failed, errno: %d", errno); + + pid =3D fork(); + TEST_ASSERT(pid >=3D 0, "fork failed, errno: %d", errno); + + if (pid > 0) { + struct kvm_vm *vm; + + close(socks[1]); + + vm =3D vm_create_barebones(); + + send_fd(socks[0], vm->fd); + close(socks[0]); + + /* Drop *ALL* refs to this VM. */ + close(vm->fd); + close(vm->kvm_fd); + if (vm->stats.fd >=3D 0) + close(vm->stats.fd); + + pthread_barrier_wait(barrier); + + /* Trigger the exit_mm() side of the race. */ + _exit(0); + } else { + int vm_fd; + + close(socks[0]); + + vm_fd =3D recv_fd(socks[1]); + close(socks[1]); + + pthread_barrier_wait(barrier); + + /* Drop the final ref of the VM, triggering the kvm_destroy_vm() + * side of the race. */ + close(vm_fd); + } + + return 0; +} --=20 2.54.0.545.g6539524ca2-goog