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, 41 insertions, 0 deletions

diff --git a/include/crypto/hash_info.h b/include/crypto/hash_info.h
new file mode 100644
index 000000000..d6927739f
--- /dev/null
+++ b/include/crypto/hash_info.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Hash Info: Hash algorithms information
+ *
+ * Copyright (c) 2013 Dmitry Kasatkin <d.kasatkin@samsung.com>
+ */
+
+#ifndef _CRYPTO_HASH_INFO_H
+#define _CRYPTO_HASH_INFO_H
+
+#include <crypto/sha1.h>
+#include <crypto/sha2.h>
+#include <crypto/sha3.h>
+#include <crypto/md5.h>
+#include <crypto/streebog.h>
+
+#include <uapi/linux/hash_info.h>
+
+/* not defined in include/crypto/ */
+#define RMD128_DIGEST_SIZE      16
+#define RMD160_DIGEST_SIZE	20
+#define RMD256_DIGEST_SIZE      32
+#define RMD320_DIGEST_SIZE      40
+
+/* not defined in include/crypto/ */
+#define WP512_DIGEST_SIZE	64
+#define WP384_DIGEST_SIZE	48
+#define WP256_DIGEST_SIZE	32
+
+/* not defined in include/crypto/ */
+#define TGR128_DIGEST_SIZE 16
+#define TGR160_DIGEST_SIZE 20
+#define TGR192_DIGEST_SIZE 24
+
+/* not defined in include/crypto/ */
+#define SM3256_DIGEST_SIZE 32
+
+extern const char *const hash_algo_name[HASH_ALGO__LAST];
+extern const int hash_digest_size[HASH_ALGO__LAST];
+
+#endif /* _CRYPTO_HASH_INFO_H */