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, 234 insertions, 0 deletions

diff --git a/include/trace/events/devlink.h b/include/trace/events/devlink.h
new file mode 100644
index 000000000..4f8edf77d
--- /dev/null
+++ b/include/trace/events/devlink.h
@@ -0,0 +1,234 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if IS_ENABLED(CONFIG_NET_DEVLINK)
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM devlink
+
+#if !defined(_TRACE_DEVLINK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DEVLINK_H
+
+#include <linux/device.h>
+#include <net/devlink.h>
+#include <linux/tracepoint.h>
+
+/*
+ * Tracepoint for devlink hardware message:
+ */
+TRACE_EVENT(devlink_hwmsg,
+	TP_PROTO(const struct devlink *devlink, bool incoming,
+		 unsigned long type, const u8 *buf, size_t len),
+
+	TP_ARGS(devlink, incoming, type, buf, len),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__field(bool, incoming)
+		__field(unsigned long, type)
+		__dynamic_array(u8, buf, len)
+		__field(size_t, len)
+	),
+
+	TP_fast_assign(
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__entry->incoming = incoming;
+		__entry->type = type;
+		memcpy(__get_dynamic_array(buf), buf, len);
+		__entry->len = len;
+	),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s incoming=%d type=%lu buf=0x[%*phD] len=%zu",
+		  __get_str(bus_name), __get_str(dev_name),
+		  __get_str(driver_name), __entry->incoming, __entry->type,
+		  (int) __entry->len, __get_dynamic_array(buf), __entry->len)
+);
+
+/*
+ * Tracepoint for devlink hardware error:
+ */
+TRACE_EVENT(devlink_hwerr,
+	TP_PROTO(const struct devlink *devlink, int err, const char *msg),
+
+	TP_ARGS(devlink, err, msg),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__field(int, err)
+		__string(msg, msg)
+		),
+
+	TP_fast_assign(
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__entry->err = err;
+		__assign_str(msg);
+		),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s err=%d %s",
+			__get_str(bus_name), __get_str(dev_name),
+			__get_str(driver_name), __entry->err, __get_str(msg))
+);
+
+/*
+ * Tracepoint for devlink health message:
+ */
+TRACE_EVENT(devlink_health_report,
+	TP_PROTO(const struct devlink *devlink, const char *reporter_name,
+		 const char *msg),
+
+	TP_ARGS(devlink, reporter_name, msg),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__string(reporter_name, reporter_name)
+		__string(msg, msg)
+	),
+
+	TP_fast_assign(
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__assign_str(reporter_name);
+		__assign_str(msg);
+	),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s reporter_name=%s: %s",
+		  __get_str(bus_name), __get_str(dev_name),
+		  __get_str(driver_name), __get_str(reporter_name),
+		  __get_str(msg))
+);
+
+/*
+ * Tracepoint for devlink health recover aborted message:
+ */
+TRACE_EVENT(devlink_health_recover_aborted,
+	TP_PROTO(const struct devlink *devlink, const char *reporter_name,
+		 bool health_state, u64 time_since_last_recover),
+
+	TP_ARGS(devlink, reporter_name, health_state, time_since_last_recover),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__string(reporter_name, reporter_name)
+		__field(bool, health_state)
+		__field(u64, time_since_last_recover)
+	),
+
+	TP_fast_assign(
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__assign_str(reporter_name);
+		__entry->health_state = health_state;
+		__entry->time_since_last_recover = time_since_last_recover;
+	),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s reporter_name=%s: health_state=%d time_since_last_recover=%llu recover aborted",
+		  __get_str(bus_name), __get_str(dev_name),
+		  __get_str(driver_name), __get_str(reporter_name),
+		  __entry->health_state,
+		  __entry->time_since_last_recover)
+);
+
+/*
+ * Tracepoint for devlink health reporter state update:
+ */
+TRACE_EVENT(devlink_health_reporter_state_update,
+	TP_PROTO(const struct devlink *devlink, const char *reporter_name,
+		 bool new_state),
+
+	TP_ARGS(devlink, reporter_name, new_state),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__string(reporter_name, reporter_name)
+		__field(u8, new_state)
+	),
+
+	TP_fast_assign(
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__assign_str(reporter_name);
+		__entry->new_state = new_state;
+	),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s reporter_name=%s: new_state=%d",
+		  __get_str(bus_name), __get_str(dev_name),
+		  __get_str(driver_name), __get_str(reporter_name),
+		  __entry->new_state)
+);
+
+/*
+ * Tracepoint for devlink packet trap:
+ */
+TRACE_EVENT(devlink_trap_report,
+	TP_PROTO(const struct devlink *devlink, struct sk_buff *skb,
+		 const struct devlink_trap_metadata *metadata),
+
+	TP_ARGS(devlink, skb, metadata),
+
+	TP_STRUCT__entry(
+		__string(bus_name, devlink_bus_name(devlink))
+		__string(dev_name, devlink_dev_name(devlink))
+		__string(driver_name, devlink_dev_driver_name(devlink))
+		__string(trap_name, metadata->trap_name)
+		__string(trap_group_name, metadata->trap_group_name)
+		__array(char, input_dev_name, IFNAMSIZ)
+	),
+
+	TP_fast_assign(
+		struct net_device *input_dev = metadata->input_dev;
+
+		__assign_str(bus_name);
+		__assign_str(dev_name);
+		__assign_str(driver_name);
+		__assign_str(trap_name);
+		__assign_str(trap_group_name);
+		strscpy(__entry->input_dev_name, input_dev ? input_dev->name : "NULL", IFNAMSIZ);
+	),
+
+	TP_printk("bus_name=%s dev_name=%s driver_name=%s trap_name=%s "
+		  "trap_group_name=%s input_dev_name=%s", __get_str(bus_name),
+		  __get_str(dev_name), __get_str(driver_name),
+		  __get_str(trap_name), __get_str(trap_group_name),
+		  __entry->input_dev_name)
+);
+
+#endif /* _TRACE_DEVLINK_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
+
+#else /* CONFIG_NET_DEVLINK */
+
+#if !defined(_TRACE_DEVLINK_H)
+#define _TRACE_DEVLINK_H
+
+#include <net/devlink.h>
+
+static inline void trace_devlink_hwmsg(const struct devlink *devlink,
+				       bool incoming, unsigned long type,
+				       const u8 *buf, size_t len)
+{
+}
+
+static inline void trace_devlink_hwerr(const struct devlink *devlink,
+				       int err, const char *msg)
+{
+}
+#endif /* _TRACE_DEVLINK_H */
+
+#endif