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, 43 insertions, 0 deletions

diff --git a/include/sound/sof/debug.h b/include/sound/sof/debug.h
new file mode 100644
index 000000000..8b308d7e5
--- /dev/null
+++ b/include/sound/sof/debug.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * Copyright(c) 2020 Intel Corporation
+ *
+ * Author: Karol Trzcinski <karolx.trzcinski@linux.intel.com>
+ */
+
+#ifndef __INCLUDE_SOUND_SOF_DEBUG_H__
+#define __INCLUDE_SOUND_SOF_DEBUG_H__
+
+#include <sound/sof/header.h>
+
+/** ABI3.18 */
+enum sof_ipc_dbg_mem_zone {
+	SOF_IPC_MEM_ZONE_SYS		= 0,	/**< System zone */
+	SOF_IPC_MEM_ZONE_SYS_RUNTIME	= 1,	/**< System-runtime zone */
+	SOF_IPC_MEM_ZONE_RUNTIME	= 2,	/**< Runtime zone */
+	SOF_IPC_MEM_ZONE_BUFFER		= 3,	/**< Buffer zone */
+	SOF_IPC_MEM_ZONE_RUNTIME_SHARED	= 4,	/**< System runtime zone */
+	SOF_IPC_MEM_ZONE_SYS_SHARED	= 5,	/**< System shared zone */
+};
+
+/** ABI3.18 */
+struct sof_ipc_dbg_mem_usage_elem {
+	uint32_t zone;		/**< see sof_ipc_dbg_mem_zone */
+	uint32_t id;		/**< heap index within zone */
+	uint32_t used;		/**< number of bytes used in zone */
+	uint32_t free;		/**< number of bytes free to use within zone */
+	uint32_t reserved;	/**< for future use */
+} __packed;
+
+/** ABI3.18 */
+struct sof_ipc_dbg_mem_usage {
+	struct sof_ipc_reply rhdr;			/**< generic IPC reply header */
+	uint32_t reserved[4];				/**< reserved for future use */
+	uint32_t num_elems;				/**< elems[] counter */
+	struct sof_ipc_dbg_mem_usage_elem elems[];	/**< memory usage information */
+} __packed;
+
+#endif