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Thu, 30 Jul 2026 02:17:16 -0700 (PDT) From: Guidong Han <2045gemini@gmail.com> To: Anup Patel , Atish Patra Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Naveed Khan , kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guidong Han <2045gemini@gmail.com> Subject: [PATCH v2] RISC-V: KVM: Fix PMU event info array size overflow Date: Thu, 30 Jul 2026 17:17:10 +0800 Message-ID: <20260730091710.1366757-1-2045gemini@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260718153620.829378-1-2045gemini@gmail.com> References: <20260718153620.829378-1-2045gemini@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit SBI PMU EVENT_GET_INFO stores guest-controlled num_events * sizeof(*einfo) in an int. On RV64, num_events = 0x10000001 makes 0x100000010 truncate to 16. KVM then allocates one entry but loops over the original num_events, causing out-of-bounds reads and writes. A nested guest triggered: BUG: KASAN: slab-out-of-bounds in kvm_riscv_vcpu_pmu_event_info+0xa4/0x142 Read of size 4 at addr ff600000074d46b0 by task init/1 Call Trace: [] kvm_riscv_vcpu_pmu_event_info+0xa4/0x142 [] kvm_sbi_ext_pmu_handler+0xca/0x268 [] kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6 [] kvm_riscv_vcpu_exit+0x48c/0x540 [] kvm_arch_vcpu_ioctl_run+0x37e/0xc80 Allocated by task 1: __kmalloc_noprof+0x19e/0x4b0 kvm_riscv_vcpu_pmu_event_info+0x72/0x142 kvm_sbi_ext_pmu_handler+0xca/0x268 kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6 kvm_riscv_vcpu_exit+0x48c/0x540 kvm_arch_vcpu_ioctl_run+0x37e/0xc80 The buggy address is located 0 bytes to the right of allocated 16-byte region [ff600000074d46a0, ff600000074d46b0) Store the shared-memory size in size_t and reject multiplication overflow. Allocate the guest-driven array with GFP_KERNEL_ACCOUNT so it is charged to kmemcg, and use __GFP_NOWARN to suppress allocation failure warnings. Use kvcalloc() to allow vmalloc fallback and an unsigned long loop index to match num_events. Reported-by: Naveed Khan Closes: https://lore.kernel.org/kvm/178345245327.72065.13249716450708539854@digiscrypt.com/ Fixes: e309fd113b9f ("RISC-V: KVM: Implement get event info function") Cc: stable@vger.kernel.org Signed-off-by: Guidong Han <2045gemini@gmail.com> --- Changes in v2: - Use an accounted, no-warning kvcalloc() allocation and kvfree(), as suggested by Sashiko. - Naveed Khan reported the issue before v1. I missed his report at the time, so add Reported-by and Closes tags to credit him. Link to v1: https://lore.kernel.org/kvm/20260718153620.829378-1-2045gemini@gmail.com/ --- arch/riscv/kvm/vcpu_pmu.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c index bb46dcbfb24d..8e1f6abb84e2 100644 --- a/arch/riscv/kvm/vcpu_pmu.c +++ b/arch/riscv/kvm/vcpu_pmu.c @@ -12,7 +12,9 @@ #include #include #include +#include #include +#include #include #include #include @@ -479,13 +481,14 @@ int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low unsigned long flags, struct kvm_vcpu_sbi_return *retdata) { struct riscv_pmu_event_info *einfo = NULL; - int shmem_size = num_events * sizeof(*einfo); + size_t shmem_size; gpa_t shmem; u32 eidx, etype; u64 econfig; int ret; - if (flags != 0 || (saddr_low & (SZ_16 - 1) || num_events == 0)) { + if (flags != 0 || (saddr_low & (SZ_16 - 1)) || num_events == 0 || + check_mul_overflow(num_events, sizeof(*einfo), &shmem_size)) { ret = SBI_ERR_INVALID_PARAM; goto out; } @@ -500,7 +503,8 @@ int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low } } - einfo = kzalloc(shmem_size, GFP_KERNEL); + einfo = kvcalloc(num_events, sizeof(*einfo), + GFP_KERNEL_ACCOUNT | __GFP_NOWARN); if (!einfo) { ret = SBI_ERR_FAILURE; goto out; @@ -512,7 +516,7 @@ int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low goto free_mem; } - for (int i = 0; i < num_events; i++) { + for (unsigned long i = 0; i < num_events; i++) { eidx = einfo[i].event_idx; etype = kvm_pmu_get_perf_event_type(eidx); econfig = kvm_pmu_get_perf_event_config(eidx, einfo[i].event_data); @@ -525,7 +529,7 @@ int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low ret = SBI_ERR_INVALID_ADDRESS; free_mem: - kfree(einfo); + kvfree(einfo); out: retdata->err_val = ret; -- 2.43.0