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, 29 insertions, 0 deletions

diff --git a/net/wireless/ethtool.c b/net/wireless/ethtool.c
new file mode 100644
index 000000000..46e4317cb
--- /dev/null
+++ b/net/wireless/ethtool.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/utsname.h>
+#include <net/cfg80211.h>
+#include "core.h"
+#include "rdev-ops.h"
+
+void cfg80211_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct device *pdev = wiphy_dev(wdev->wiphy);
+
+	if (pdev->driver)
+		strscpy(info->driver, pdev->driver->name,
+			sizeof(info->driver));
+	else
+		strscpy(info->driver, "N/A", sizeof(info->driver));
+
+	strscpy(info->version, init_utsname()->release, sizeof(info->version));
+
+	if (wdev->wiphy->fw_version[0])
+		strscpy(info->fw_version, wdev->wiphy->fw_version,
+			sizeof(info->fw_version));
+	else
+		strscpy(info->fw_version, "N/A", sizeof(info->fw_version));
+
+	strscpy(info->bus_info, dev_name(pdev),
+		sizeof(info->bus_info));
+}
+EXPORT_SYMBOL(cfg80211_get_drvinfo);