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, 55 insertions, 0 deletions

diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
new file mode 100644
index 000000000..07db37332
--- /dev/null
+++ b/security/ipe/hooks.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_HOOKS_H
+#define _IPE_HOOKS_H
+
+#include <linux/fs.h>
+#include <linux/binfmts.h>
+#include <linux/security.h>
+#include <linux/blk_types.h>
+#include <linux/fsverity.h>
+
+enum ipe_hook_type {
+	IPE_HOOK_BPRM_CHECK = 0,
+	IPE_HOOK_BPRM_CREDS_FOR_EXEC,
+	IPE_HOOK_MMAP,
+	IPE_HOOK_MPROTECT,
+	IPE_HOOK_KERNEL_READ,
+	IPE_HOOK_KERNEL_LOAD,
+	__IPE_HOOK_MAX
+};
+
+#define IPE_HOOK_INVALID __IPE_HOOK_MAX
+
+int ipe_bprm_check_security(struct linux_binprm *bprm);
+
+int ipe_bprm_creds_for_exec(struct linux_binprm *bprm);
+
+int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
+		  unsigned long flags);
+
+int ipe_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
+		      unsigned long prot);
+
+int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
+			 bool contents);
+
+int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents);
+
+void ipe_unpack_initramfs(void);
+
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+void ipe_bdev_free_security(struct block_device *bdev);
+
+int ipe_bdev_setintegrity(struct block_device *bdev, enum lsm_integrity_type type,
+			  const void *value, size_t len);
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
+#ifdef CONFIG_IPE_PROP_FS_VERITY_BUILTIN_SIG
+int ipe_inode_setintegrity(const struct inode *inode, enum lsm_integrity_type type,
+			   const void *value, size_t size);
+#endif /* CONFIG_IPE_PROP_FS_VERITY_BUILTIN_SIG */
+
+#endif /* _IPE_HOOKS_H */