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, 45 insertions, 0 deletions

diff --git a/net/mac80211/debugfs_netdev.h b/net/mac80211/debugfs_netdev.h
new file mode 100644
index 000000000..a02ec0a41
--- /dev/null
+++ b/net/mac80211/debugfs_netdev.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Portions:
+ * Copyright (C) 2023 Intel Corporation
+ */
+/* routines exported for debugfs handling */
+
+#ifndef __IEEE80211_DEBUGFS_NETDEV_H
+#define __IEEE80211_DEBUGFS_NETDEV_H
+
+#include "ieee80211_i.h"
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+void ieee80211_debugfs_remove_netdev(struct ieee80211_sub_if_data *sdata);
+void ieee80211_debugfs_rename_netdev(struct ieee80211_sub_if_data *sdata);
+void ieee80211_debugfs_recreate_netdev(struct ieee80211_sub_if_data *sdata,
+				       bool mld_vif);
+
+void ieee80211_link_debugfs_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link);
+
+void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link);
+#else
+static inline void ieee80211_debugfs_remove_netdev(
+	struct ieee80211_sub_if_data *sdata)
+{}
+static inline void ieee80211_debugfs_rename_netdev(
+	struct ieee80211_sub_if_data *sdata)
+{}
+static inline void ieee80211_debugfs_recreate_netdev(
+	struct ieee80211_sub_if_data *sdata, bool mld_vif)
+{}
+static inline void ieee80211_link_debugfs_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link)
+{}
+
+static inline void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link)
+{}
+#endif
+
+#endif /* __IEEE80211_DEBUGFS_NETDEV_H */