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Wed, 04 Mar 2026 08:22:24 -0800 (PST) Date: Wed, 4 Mar 2026 16:22:21 +0000 In-Reply-To: <20260304162222.836152-1-tabba@google.com> Mime-Version: 1.0 References: <20260304162222.836152-1-tabba@google.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260304162222.836152-2-tabba@google.com> Subject: [PATCH v1 1/2] KVM: arm64: Fix page leak in user_mem_abort() on atomic fault From: Fuad Tabba To: kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, yangyicong@hisilicon.com, wangzhou1@hisilicon.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260304_162226_957394_E97388A4 X-CRM114-Status: GOOD ( 14.93 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org When a guest performs an atomic/exclusive operation on memory lacking the required attributes, user_mem_abort() injects a data abort and returns early. However, it fails to release the reference to the host page acquired via __kvm_faultin_pfn(). A malicious guest could repeatedly trigger this fault, leaking host page references and eventually causing host memory exhaustion (OOM). Fix this by consolidating the early error returns to a new out_put_page label that correctly calls kvm_release_page_unused(). Fixes: 2937aeec9dc5 ("KVM: arm64: Handle DABT caused by LS64* instructions on unsupported memory") Signed-off-by: Fuad Tabba --- arch/arm64/kvm/mmu.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index ec2eee857208..e1d6a4f591a9 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1837,10 +1837,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (exec_fault && s2_force_noncacheable) ret = -ENOEXEC; - if (ret) { - kvm_release_page_unused(page); - return ret; - } + if (ret) + goto out_put_page; /* * Guest performs atomic/exclusive operations on memory with unsupported @@ -1850,7 +1848,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, */ if (esr_fsc_is_excl_atomic_fault(kvm_vcpu_get_esr(vcpu))) { kvm_inject_dabt_excl_atomic(vcpu, kvm_vcpu_get_hfar(vcpu)); - return 1; + ret = 1; + goto out_put_page; } if (nested) @@ -1936,6 +1935,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, mark_page_dirty_in_slot(kvm, memslot, gfn); return ret != -EAGAIN ? ret : 0; + +out_put_page: + kvm_release_page_unused(page); + return ret; } /* Resolve the access fault by making the page young again. */ -- 2.53.0.473.g4a7958ca14-goog