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, 134 insertions, 0 deletions

diff --git a/crypto/des_generic.c b/crypto/des_generic.c
new file mode 100644
index 000000000..fce341400
--- /dev/null
+++ b/crypto/des_generic.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API.
+ *
+ * DES & Triple DES EDE Cipher Algorithms.
+ *
+ * Copyright (c) 2005 Dag Arne Osvik <da@osvik.no>
+ */
+
+#include <asm/byteorder.h>
+#include <crypto/algapi.h>
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+
+#include <crypto/internal/des.h>
+
+static int des_setkey(struct crypto_tfm *tfm, const u8 *key,
+		      unsigned int keylen)
+{
+	struct des_ctx *dctx = crypto_tfm_ctx(tfm);
+	int err;
+
+	err = des_expand_key(dctx, key, keylen);
+	if (err == -ENOKEY) {
+		if (crypto_tfm_get_flags(tfm) & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)
+			err = -EINVAL;
+		else
+			err = 0;
+	}
+	if (err)
+		memset(dctx, 0, sizeof(*dctx));
+	return err;
+}
+
+static void crypto_des_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
+{
+	const struct des_ctx *dctx = crypto_tfm_ctx(tfm);
+
+	des_encrypt(dctx, dst, src);
+}
+
+static void crypto_des_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
+{
+	const struct des_ctx *dctx = crypto_tfm_ctx(tfm);
+
+	des_decrypt(dctx, dst, src);
+}
+
+static int des3_ede_setkey(struct crypto_tfm *tfm, const u8 *key,
+			   unsigned int keylen)
+{
+	struct des3_ede_ctx *dctx = crypto_tfm_ctx(tfm);
+	int err;
+
+	err = des3_ede_expand_key(dctx, key, keylen);
+	if (err == -ENOKEY) {
+		if (crypto_tfm_get_flags(tfm) & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)
+			err = -EINVAL;
+		else
+			err = 0;
+	}
+	if (err)
+		memset(dctx, 0, sizeof(*dctx));
+	return err;
+}
+
+static void crypto_des3_ede_encrypt(struct crypto_tfm *tfm, u8 *dst,
+				    const u8 *src)
+{
+	const struct des3_ede_ctx *dctx = crypto_tfm_ctx(tfm);
+
+	des3_ede_encrypt(dctx, dst, src);
+}
+
+static void crypto_des3_ede_decrypt(struct crypto_tfm *tfm, u8 *dst,
+				    const u8 *src)
+{
+	const struct des3_ede_ctx *dctx = crypto_tfm_ctx(tfm);
+
+	des3_ede_decrypt(dctx, dst, src);
+}
+
+static struct crypto_alg des_algs[2] = { {
+	.cra_name		=	"des",
+	.cra_driver_name	=	"des-generic",
+	.cra_priority		=	100,
+	.cra_flags		=	CRYPTO_ALG_TYPE_CIPHER,
+	.cra_blocksize		=	DES_BLOCK_SIZE,
+	.cra_ctxsize		=	sizeof(struct des_ctx),
+	.cra_module		=	THIS_MODULE,
+	.cra_u			=	{ .cipher = {
+	.cia_min_keysize	=	DES_KEY_SIZE,
+	.cia_max_keysize	=	DES_KEY_SIZE,
+	.cia_setkey		=	des_setkey,
+	.cia_encrypt		=	crypto_des_encrypt,
+	.cia_decrypt		=	crypto_des_decrypt } }
+}, {
+	.cra_name		=	"des3_ede",
+	.cra_driver_name	=	"des3_ede-generic",
+	.cra_priority		=	100,
+	.cra_flags		=	CRYPTO_ALG_TYPE_CIPHER,
+	.cra_blocksize		=	DES3_EDE_BLOCK_SIZE,
+	.cra_ctxsize		=	sizeof(struct des3_ede_ctx),
+	.cra_module		=	THIS_MODULE,
+	.cra_u			=	{ .cipher = {
+	.cia_min_keysize	=	DES3_EDE_KEY_SIZE,
+	.cia_max_keysize	=	DES3_EDE_KEY_SIZE,
+	.cia_setkey		=	des3_ede_setkey,
+	.cia_encrypt		=	crypto_des3_ede_encrypt,
+	.cia_decrypt		=	crypto_des3_ede_decrypt } }
+} };
+
+static int __init des_generic_mod_init(void)
+{
+	return crypto_register_algs(des_algs, ARRAY_SIZE(des_algs));
+}
+
+static void __exit des_generic_mod_fini(void)
+{
+	crypto_unregister_algs(des_algs, ARRAY_SIZE(des_algs));
+}
+
+module_init(des_generic_mod_init);
+module_exit(des_generic_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("DES & Triple DES EDE Cipher Algorithms");
+MODULE_AUTHOR("Dag Arne Osvik <da@osvik.no>");
+MODULE_ALIAS_CRYPTO("des");
+MODULE_ALIAS_CRYPTO("des-generic");
+MODULE_ALIAS_CRYPTO("des3_ede");
+MODULE_ALIAS_CRYPTO("des3_ede-generic");