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([210.73.43.101]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8231864489csm6108340b3a.9.2026.01.24.22.04.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Jan 2026 22:04:49 -0800 (PST) From: Jiakai Xu X-Google-Original-From: Jiakai Xu To: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org Cc: Alexandre Ghiti , Albert Ou , Palmer Dabbelt , Paul Walmsley , Atish Patra , Anup Patel , Jiakai Xu Subject: [PATCH] RISC-V: KVM: Fix null pointer dereference in kvm_riscv_aia_imsic_has_attr Date: Sun, 25 Jan 2026 06:04:41 +0000 Message-Id: <20260125060441.2437515-1-xujiakai2025@iscas.ac.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a null pointer check for imsic_state before dereferencing it in kvm_riscv_aia_imsic_has_attr(). While the function checks that the vcpu exists, it doesn't verify that the vcpu's imsic_state has been initialized, leading to a null pointer dereference when accessed. This issue was discovered during fuzzing of RISC-V KVM code. The crash occurs when userspace calls KVM_HAS_DEVICE_ATTR ioctl on an AIA IMSIC device before the IMSIC state has been fully initialized for a vcpu. The crash manifests as: Unable to handle kernel paging request at virtual address=20 dfffffff00000001 ... epc : kvm_riscv_aia_imsic_has_attr+0x464/0x50e=20 arch/riscv/kvm/aia_imsic.c:998 ... kvm_riscv_aia_imsic_has_attr+0x464/0x50e arch/riscv/kvm/aia_imsic.c:998 aia_has_attr+0x128/0x2bc arch/riscv/kvm/aia_device.c:471 kvm_device_ioctl_attr virt/kvm/kvm_main.c:4722 [inline] kvm_device_ioctl+0x296/0x374 virt/kvm/kvm_main.c:4739 ... The fix adds a check to return -ENODEV if imsic_state is NULL, which is consistent with other error handling in the function and prevents the null pointer dereference. Reproducer and detailed analysis available at: https://github.com/j1akai/temp/tree/main/20260125 Signed-off-by: Jiakai Xu Reviewed-by: Anup Patel --- arch/riscv/kvm/aia_imsic.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c index e597e86491c3b..9c58a66068447 100644 --- a/arch/riscv/kvm/aia_imsic.c +++ b/arch/riscv/kvm/aia_imsic.c @@ -995,6 +995,9 @@ int kvm_riscv_aia_imsic_has_attr(struct kvm *kvm, unsig= ned long type) =20 isel =3D KVM_DEV_RISCV_AIA_IMSIC_GET_ISEL(type); imsic =3D vcpu->arch.aia_context.imsic_state; + if (!imsic) + return -ENODEV; + return imsic_mrif_isel_check(imsic->nr_eix, isel); } =20 --=20 2.34.1