ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

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 <xiqi2@huawei.com>

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) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 137 insertions, 0 deletions

diff --git a/drivers/firmware/imx/misc.c b/drivers/firmware/imx/misc.c
new file mode 100644
index 000000000..d073cb3ce
--- /dev/null
+++ b/drivers/firmware/imx/misc.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Copyright 2017~2018 NXP
+ *  Author: Dong Aisheng <aisheng.dong@nxp.com>
+ *
+ * File containing client-side RPC functions for the MISC service. These
+ * function are ported to clients that communicate to the SC.
+ *
+ */
+
+#include <linux/firmware/imx/svc/misc.h>
+
+struct imx_sc_msg_req_misc_set_ctrl {
+	struct imx_sc_rpc_msg hdr;
+	u32 ctrl;
+	u32 val;
+	u16 resource;
+} __packed __aligned(4);
+
+struct imx_sc_msg_req_cpu_start {
+	struct imx_sc_rpc_msg hdr;
+	u32 address_hi;
+	u32 address_lo;
+	u16 resource;
+	u8 enable;
+} __packed __aligned(4);
+
+struct imx_sc_msg_req_misc_get_ctrl {
+	struct imx_sc_rpc_msg hdr;
+	u32 ctrl;
+	u16 resource;
+} __packed __aligned(4);
+
+struct imx_sc_msg_resp_misc_get_ctrl {
+	struct imx_sc_rpc_msg hdr;
+	u32 val;
+} __packed __aligned(4);
+
+/*
+ * This function sets a miscellaneous control value.
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in]     resource    resource the control is associated with
+ * @param[in]     ctrl        control to change
+ * @param[in]     val         value to apply to the control
+ *
+ * @return Returns 0 for success and < 0 for errors.
+ */
+
+int imx_sc_misc_set_control(struct imx_sc_ipc *ipc, u32 resource,
+			    u8 ctrl, u32 val)
+{
+	struct imx_sc_msg_req_misc_set_ctrl msg;
+	struct imx_sc_rpc_msg *hdr = &msg.hdr;
+
+	hdr->ver = IMX_SC_RPC_VERSION;
+	hdr->svc = (uint8_t)IMX_SC_RPC_SVC_MISC;
+	hdr->func = (uint8_t)IMX_SC_MISC_FUNC_SET_CONTROL;
+	hdr->size = 4;
+
+	msg.ctrl = ctrl;
+	msg.val = val;
+	msg.resource = resource;
+
+	return imx_scu_call_rpc(ipc, &msg, true);
+}
+EXPORT_SYMBOL(imx_sc_misc_set_control);
+
+/*
+ * This function gets a miscellaneous control value.
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in]     resource    resource the control is associated with
+ * @param[in]     ctrl        control to get
+ * @param[out]    val         pointer to return the control value
+ *
+ * @return Returns 0 for success and < 0 for errors.
+ */
+
+int imx_sc_misc_get_control(struct imx_sc_ipc *ipc, u32 resource,
+			    u8 ctrl, u32 *val)
+{
+	struct imx_sc_msg_req_misc_get_ctrl msg;
+	struct imx_sc_msg_resp_misc_get_ctrl *resp;
+	struct imx_sc_rpc_msg *hdr = &msg.hdr;
+	int ret;
+
+	hdr->ver = IMX_SC_RPC_VERSION;
+	hdr->svc = (uint8_t)IMX_SC_RPC_SVC_MISC;
+	hdr->func = (uint8_t)IMX_SC_MISC_FUNC_GET_CONTROL;
+	hdr->size = 3;
+
+	msg.ctrl = ctrl;
+	msg.resource = resource;
+
+	ret = imx_scu_call_rpc(ipc, &msg, true);
+	if (ret)
+		return ret;
+
+	resp = (struct imx_sc_msg_resp_misc_get_ctrl *)&msg;
+	if (val != NULL)
+		*val = resp->val;
+
+	return 0;
+}
+EXPORT_SYMBOL(imx_sc_misc_get_control);
+
+/*
+ * This function starts/stops a CPU identified by @resource
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in]     resource    resource the control is associated with
+ * @param[in]     enable      true for start, false for stop
+ * @param[in]     phys_addr   initial instruction address to be executed
+ *
+ * @return Returns 0 for success and < 0 for errors.
+ */
+int imx_sc_pm_cpu_start(struct imx_sc_ipc *ipc, u32 resource,
+			bool enable, u64 phys_addr)
+{
+	struct imx_sc_msg_req_cpu_start msg;
+	struct imx_sc_rpc_msg *hdr = &msg.hdr;
+
+	hdr->ver = IMX_SC_RPC_VERSION;
+	hdr->svc = IMX_SC_RPC_SVC_PM;
+	hdr->func = IMX_SC_PM_FUNC_CPU_START;
+	hdr->size = 4;
+
+	msg.address_hi = phys_addr >> 32;
+	msg.address_lo = phys_addr;
+	msg.resource = resource;
+	msg.enable = enable;
+
+	return imx_scu_call_rpc(ipc, &msg, true);
+}
+EXPORT_SYMBOL(imx_sc_pm_cpu_start);