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(unknown [210.73.43.101]) by APP-05 (Coremail) with SMTP id zQCowAA3zRDehHxpX_wMBw--.48711S2; Fri, 30 Jan 2026 18:15:58 +0800 (CST) 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 , Jiakai Xu Subject: [PATCH] RISC-V: KVM: Fix null pointer dereference in kvm_riscv_vcpu_aia_rmw_topei() Date: Fri, 30 Jan 2026 10:15:57 +0000 Message-Id: <20260130101557.1314385-1-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 X-CM-TRANSID: zQCowAA3zRDehHxpX_wMBw--.48711S2 X-Coremail-Antispam: 1UD129KBjvJXoW7WFyUuryxKr4Dtr47Cry5twb_yoW8Zw45pF sxCrsa9r48XFWxCasIywn7Xr40gr4vkF1aqr98urW5Gr4UKFWFyr1vgay7XFW8JF10vwn2 yr4UCFW8uF1UJw7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPj14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26ryj6F1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4j 6r4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAac4AC62xK8xCEY4vEwIxC4wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC 0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUAVWUtwAv7VC2z280aVAFwI0_Gr0_Cr 1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IE rcIFxwACI402YVCY1x02628vn2kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCY02Avz4vE14 v_Gw1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AK xVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrx kI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v2 6r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8Jw CI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfU5o7KDUUU U X-CM-SenderInfo: 50xmxthndljiysv6x2xfdvhtffof0/1tbiBgwDCWl8VkKsNAAAsZ Content-Type: text/plain; charset="utf-8" kvm_riscv_vcpu_aia_rmw_topei() assumes that the per-vCPU IMSIC state has been initialized once AIA is reported as available and initialized at the VM level. This assumption does not always hold. Under fuzzed ioctl sequences, a guest may access the IMSIC TOPEI CSR before the vCPU IMSIC state is set up. In this case, vcpu->arch.aia_context.imsic_state is still NULL, and the TOPEI RMW path dereferences it unconditionally, leading to a host kernel crash. The crash manifests as: Unable to handle kernel paging request at virtual address dfffffff0000000e ... kvm_riscv_vcpu_aia_imsic_rmw arch/riscv/kvm/aia_imsic.c:909 kvm_riscv_vcpu_aia_rmw_topei arch/riscv/kvm/aia.c:231 csr_insn arch/riscv/kvm/vcpu_insn.c:208 system_opcode_insn arch/riscv/kvm/vcpu_insn.c:281 kvm_riscv_vcpu_virtual_insn arch/riscv/kvm/vcpu_insn.c:355 kvm_riscv_vcpu_exit arch/riscv/kvm/vcpu_exit.c:230 kvm_arch_vcpu_ioctl_run arch/riscv/kvm/vcpu.c:1008 ... Fix this by explicitly checking whether the vCPU IMSIC state has been initialized before handling TOPEI CSR accesses. If not, forward the CSR emulation to user space. Fixes: 2f4d58f7635ae ("RISC-V: KVM: Virtualize per-HART AIA CSRs") Signed-off-by: Jiakai Xu Signed-off-by: Jiakai Xu --- arch/riscv/kvm/aia.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c index dad3181856600..c176b960d8a40 100644 --- a/arch/riscv/kvm/aia.c +++ b/arch/riscv/kvm/aia.c @@ -228,6 +228,10 @@ int kvm_riscv_vcpu_aia_rmw_topei(struct kvm_vcpu *vcpu, if (!kvm_riscv_aia_initialized(vcpu->kvm)) return KVM_INSN_EXIT_TO_USER_SPACE; =20 + /* If IMSIC vCPU state not initialized then forward to user space */ + if (!vcpu->arch.aia_context.imsic_state) + return KVM_INSN_EXIT_TO_USER_SPACE; + return kvm_riscv_vcpu_aia_imsic_rmw(vcpu, KVM_RISCV_AIA_IMSIC_TOPEI, val, new_val, wr_mask); } --=20 2.34.1