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, 140 insertions, 0 deletions

diff --git a/crypto/kpp.c b/crypto/kpp.c
new file mode 100644
index 000000000..522c352a0
--- /dev/null
+++ b/crypto/kpp.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Key-agreement Protocol Primitives (KPP)
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ */
+
+#include <crypto/internal/kpp.h>
+#include <linux/cryptouser.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/string.h>
+#include <net/netlink.h>
+
+#include "internal.h"
+
+static int __maybe_unused crypto_kpp_report(
+	struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct crypto_report_kpp rkpp = {
+		.type = "kpp",
+	};
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_KPP, sizeof(rkpp), &rkpp);
+}
+
+static void __maybe_unused crypto_kpp_show(struct seq_file *m,
+					   struct crypto_alg *alg)
+{
+	seq_puts(m, "type         : kpp\n");
+}
+
+static void crypto_kpp_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_kpp *kpp = __crypto_kpp_tfm(tfm);
+	struct kpp_alg *alg = crypto_kpp_alg(kpp);
+
+	alg->exit(kpp);
+}
+
+static int crypto_kpp_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_kpp *kpp = __crypto_kpp_tfm(tfm);
+	struct kpp_alg *alg = crypto_kpp_alg(kpp);
+
+	if (alg->exit)
+		kpp->base.exit = crypto_kpp_exit_tfm;
+
+	if (alg->init)
+		return alg->init(kpp);
+
+	return 0;
+}
+
+static void crypto_kpp_free_instance(struct crypto_instance *inst)
+{
+	struct kpp_instance *kpp = kpp_instance(inst);
+
+	kpp->free(kpp);
+}
+
+static const struct crypto_type crypto_kpp_type = {
+	.extsize = crypto_alg_extsize,
+	.init_tfm = crypto_kpp_init_tfm,
+	.free = crypto_kpp_free_instance,
+#ifdef CONFIG_PROC_FS
+	.show = crypto_kpp_show,
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_USER)
+	.report = crypto_kpp_report,
+#endif
+	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
+	.maskset = CRYPTO_ALG_TYPE_MASK,
+	.type = CRYPTO_ALG_TYPE_KPP,
+	.tfmsize = offsetof(struct crypto_kpp, base),
+	.algsize = offsetof(struct kpp_alg, base),
+};
+
+struct crypto_kpp *crypto_alloc_kpp(const char *alg_name, u32 type, u32 mask)
+{
+	return crypto_alloc_tfm(alg_name, &crypto_kpp_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_kpp);
+
+int crypto_grab_kpp(struct crypto_kpp_spawn *spawn,
+		    struct crypto_instance *inst,
+		    const char *name, u32 type, u32 mask)
+{
+	spawn->base.frontend = &crypto_kpp_type;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_grab_kpp);
+
+int crypto_has_kpp(const char *alg_name, u32 type, u32 mask)
+{
+	return crypto_type_has_alg(alg_name, &crypto_kpp_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_has_kpp);
+
+static void kpp_prepare_alg(struct kpp_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	base->cra_type = &crypto_kpp_type;
+	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
+	base->cra_flags |= CRYPTO_ALG_TYPE_KPP;
+}
+
+int crypto_register_kpp(struct kpp_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	kpp_prepare_alg(alg);
+	return crypto_register_alg(base);
+}
+EXPORT_SYMBOL_GPL(crypto_register_kpp);
+
+void crypto_unregister_kpp(struct kpp_alg *alg)
+{
+	crypto_unregister_alg(&alg->base);
+}
+EXPORT_SYMBOL_GPL(crypto_unregister_kpp);
+
+int kpp_register_instance(struct crypto_template *tmpl,
+			  struct kpp_instance *inst)
+{
+	if (WARN_ON(!inst->free))
+		return -EINVAL;
+
+	kpp_prepare_alg(&inst->alg);
+
+	return crypto_register_instance(tmpl, kpp_crypto_instance(inst));
+}
+EXPORT_SYMBOL_GPL(kpp_register_instance);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Key-agreement Protocol Primitives");