From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte(). If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running. Acquire mmap_write_lock() around show_pte() for user faults to fix the contention. For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications. Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock. Co-developed-by: Qi Xi Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults") Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- drivers/acpi/riscv/cppc.c | 155 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 155 insertions(+) create mode 100644 drivers/acpi/riscv/cppc.c (limited to 'drivers/acpi/riscv/cppc.c') diff --git a/drivers/acpi/riscv/cppc.c b/drivers/acpi/riscv/cppc.c new file mode 100644 index 000000000..42c1a9052 --- /dev/null +++ b/drivers/acpi/riscv/cppc.c @@ -0,0 +1,155 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Implement CPPC FFH helper routines for RISC-V. + * + * Copyright (C) 2024 Ventana Micro Systems Inc. + */ + +#include +#include +#include + +#define SBI_EXT_CPPC 0x43505043 + +/* CPPC interfaces defined in SBI spec */ +#define SBI_CPPC_PROBE 0x0 +#define SBI_CPPC_READ 0x1 +#define SBI_CPPC_READ_HI 0x2 +#define SBI_CPPC_WRITE 0x3 + +/* RISC-V FFH definitions from RISC-V FFH spec */ +#define FFH_CPPC_TYPE(r) (((r) & GENMASK_ULL(63, 60)) >> 60) +#define FFH_CPPC_SBI_REG(r) ((r) & GENMASK(31, 0)) +#define FFH_CPPC_CSR_NUM(r) ((r) & GENMASK(11, 0)) + +#define FFH_CPPC_SBI 0x1 +#define FFH_CPPC_CSR 0x2 + +struct sbi_cppc_data { + u64 val; + u32 reg; + struct sbiret ret; +}; + +static bool cppc_ext_present; + +static int __init sbi_cppc_init(void) +{ + if (sbi_spec_version >= sbi_mk_version(2, 0) && + sbi_probe_extension(SBI_EXT_CPPC) > 0) { + cppc_ext_present = true; + } else { + cppc_ext_present = false; + } + + return 0; +} +device_initcall(sbi_cppc_init); + +static void sbi_cppc_read(void *read_data) +{ + struct sbi_cppc_data *data = (struct sbi_cppc_data *)read_data; + + data->ret = sbi_ecall(SBI_EXT_CPPC, SBI_CPPC_READ, + data->reg, 0, 0, 0, 0, 0); +} + +static void sbi_cppc_write(void *write_data) +{ + struct sbi_cppc_data *data = (struct sbi_cppc_data *)write_data; + + data->ret = sbi_ecall(SBI_EXT_CPPC, SBI_CPPC_WRITE, + data->reg, data->val, 0, 0, 0, 0); +} + +static void cppc_ffh_csr_read(void *read_data) +{ + struct sbi_cppc_data *data = (struct sbi_cppc_data *)read_data; + + switch (data->reg) { + /* Support only TIME CSR for now */ + case CSR_TIME: + data->ret.value = csr_read(CSR_TIME); + data->ret.error = 0; + break; + default: + data->ret.error = -EINVAL; + break; + } +} + +static void cppc_ffh_csr_write(void *write_data) +{ + struct sbi_cppc_data *data = (struct sbi_cppc_data *)write_data; + + data->ret.error = -EINVAL; +} + +/* + * Refer to drivers/acpi/cppc_acpi.c for the description of the functions + * below. + */ +bool cpc_ffh_supported(void) +{ + return true; +} + +int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val) +{ + struct sbi_cppc_data data; + + if (WARN_ON_ONCE(irqs_disabled())) + return -EPERM; + + if (FFH_CPPC_TYPE(reg->address) == FFH_CPPC_SBI) { + if (!cppc_ext_present) + return -EINVAL; + + data.reg = FFH_CPPC_SBI_REG(reg->address); + + smp_call_function_single(cpu, sbi_cppc_read, &data, 1); + + *val = data.ret.value; + + return (data.ret.error) ? sbi_err_map_linux_errno(data.ret.error) : 0; + } else if (FFH_CPPC_TYPE(reg->address) == FFH_CPPC_CSR) { + data.reg = FFH_CPPC_CSR_NUM(reg->address); + + smp_call_function_single(cpu, cppc_ffh_csr_read, &data, 1); + + *val = data.ret.value; + + return data.ret.error; + } + + return -EINVAL; +} + +int cpc_write_ffh(int cpu, struct cpc_reg *reg, u64 val) +{ + struct sbi_cppc_data data; + + if (WARN_ON_ONCE(irqs_disabled())) + return -EPERM; + + if (FFH_CPPC_TYPE(reg->address) == FFH_CPPC_SBI) { + if (!cppc_ext_present) + return -EINVAL; + + data.reg = FFH_CPPC_SBI_REG(reg->address); + data.val = val; + + smp_call_function_single(cpu, sbi_cppc_write, &data, 1); + + return (data.ret.error) ? sbi_err_map_linux_errno(data.ret.error) : 0; + } else if (FFH_CPPC_TYPE(reg->address) == FFH_CPPC_CSR) { + data.reg = FFH_CPPC_CSR_NUM(reg->address); + data.val = val; + + smp_call_function_single(cpu, cppc_ffh_csr_write, &data, 1); + + return data.ret.error; + } + + return -EINVAL; +} -- cgit v1.3.1