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, 99 insertions, 0 deletions

diff --git a/crypto/tcrypt.h b/crypto/tcrypt.h
new file mode 100644
index 000000000..85c3f77bc
--- /dev/null
+++ b/crypto/tcrypt.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Quick & dirty crypto benchmarking module.
+ *
+ * This will only exist until we have a better benchmarking mechanism
+ * (e.g. a char device).
+ *
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ * Copyright (c) 2002 Jean-Francois Dive <jef@linuxbe.org>
+ * Copyright (c) 2007 Nokia Siemens Networks
+ */
+#ifndef _CRYPTO_TCRYPT_H
+#define _CRYPTO_TCRYPT_H
+
+struct cipher_speed_template {
+	const char *key;
+	unsigned int klen;
+};
+
+struct aead_speed_template {
+	const char *key;
+	unsigned int klen;
+};
+
+struct hash_speed {
+	unsigned int blen;	/* buffer length */
+	unsigned int plen;	/* per-update length */
+};
+
+/*
+ * DES test vectors.
+ */
+#define DES3_SPEED_VECTORS	1
+
+static struct cipher_speed_template des3_speed_template[] = {
+	{
+		.key	= "\x01\x23\x45\x67\x89\xab\xcd\xef"
+			  "\x55\x55\x55\x55\x55\x55\x55\x55"
+			  "\xfe\xdc\xba\x98\x76\x54\x32\x10",
+		.klen	= 24,
+	}
+};
+
+/*
+ * Cipher speed tests
+ */
+static u8 speed_template_8[] = {8, 0};
+static u8 speed_template_16[] = {16, 0};
+static u8 speed_template_24[] = {24, 0};
+static u8 speed_template_8_16[] = {8, 16, 0};
+static u8 speed_template_8_32[] = {8, 32, 0};
+static u8 speed_template_16_32[] = {16, 32, 0};
+static u8 speed_template_16_24_32[] = {16, 24, 32, 0};
+static u8 speed_template_20_28_36[] = {20, 28, 36, 0};
+static u8 speed_template_32_40_48[] = {32, 40, 48, 0};
+static u8 speed_template_32_48[] = {32, 48, 0};
+static u8 speed_template_32_48_64[] = {32, 48, 64, 0};
+static u8 speed_template_32_64[] = {32, 64, 0};
+static u8 speed_template_32[] = {32, 0};
+
+/*
+ * AEAD speed tests
+ */
+static u8 aead_speed_template_19[] = {19, 0};
+static u8 aead_speed_template_20_28_36[] = {20, 28, 36, 0};
+static u8 aead_speed_template_36[] = {36, 0};
+
+/*
+ * Digest speed tests
+ */
+static struct hash_speed generic_hash_speed_template[] = {
+	{ .blen = 16,	.plen = 16, },
+	{ .blen = 64,	.plen = 16, },
+	{ .blen = 64,	.plen = 64, },
+	{ .blen = 256,	.plen = 16, },
+	{ .blen = 256,	.plen = 64, },
+	{ .blen = 256,	.plen = 256, },
+	{ .blen = 1024,	.plen = 16, },
+	{ .blen = 1024,	.plen = 256, },
+	{ .blen = 1024,	.plen = 1024, },
+	{ .blen = 2048,	.plen = 16, },
+	{ .blen = 2048,	.plen = 256, },
+	{ .blen = 2048,	.plen = 1024, },
+	{ .blen = 2048,	.plen = 2048, },
+	{ .blen = 4096,	.plen = 16, },
+	{ .blen = 4096,	.plen = 256, },
+	{ .blen = 4096,	.plen = 1024, },
+	{ .blen = 4096,	.plen = 4096, },
+	{ .blen = 8192,	.plen = 16, },
+	{ .blen = 8192,	.plen = 256, },
+	{ .blen = 8192,	.plen = 1024, },
+	{ .blen = 8192,	.plen = 4096, },
+	{ .blen = 8192,	.plen = 8192, },
+
+	/* End marker */
+	{  .blen = 0,	.plen = 0, }
+};
+
+#endif	/* _CRYPTO_TCRYPT_H */