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/drivers/crypto/caam/debugfs.h b/drivers/crypto/caam/debugfs.h
new file mode 100644
index 000000000..ef238c71f
--- /dev/null
+++ b/drivers/crypto/caam/debugfs.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
+/* Copyright 2019, 2023 NXP */
+
+#ifndef CAAM_DEBUGFS_H
+#define CAAM_DEBUGFS_H
+
+struct dentry;
+struct caam_drv_private;
+struct caam_perfmon;
+
+#ifdef CONFIG_DEBUG_FS
+void caam_debugfs_init(struct caam_drv_private *ctrlpriv,
+		       struct caam_perfmon __force *perfmon, struct dentry *root);
+#else
+static inline void caam_debugfs_init(struct caam_drv_private *ctrlpriv,
+				     struct caam_perfmon __force *perfmon,
+				     struct dentry *root)
+{}
+#endif
+
+#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_CRYPTO_DEV_FSL_CAAM_CRYPTO_API_QI)
+void caam_debugfs_qi_congested(void);
+void caam_debugfs_qi_init(struct caam_drv_private *ctrlpriv);
+#else
+static inline void caam_debugfs_qi_congested(void) {}
+static inline void caam_debugfs_qi_init(struct caam_drv_private *ctrlpriv) {}
+#endif
+
+#endif /* CAAM_DEBUGFS_H */