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, 155 insertions, 0 deletions

diff --git a/include/crypto/internal/akcipher.h b/include/crypto/internal/akcipher.h
new file mode 100644
index 000000000..14ee62bc5
--- /dev/null
+++ b/include/crypto/internal/akcipher.h
@@ -0,0 +1,155 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Public Key Encryption
+ *
+ * Copyright (c) 2015, Intel Corporation
+ * Authors: Tadeusz Struk <tadeusz.struk@intel.com>
+ */
+#ifndef _CRYPTO_AKCIPHER_INT_H
+#define _CRYPTO_AKCIPHER_INT_H
+#include <crypto/akcipher.h>
+#include <crypto/algapi.h>
+
+struct akcipher_instance {
+	void (*free)(struct akcipher_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct akcipher_alg, base)];
+			struct crypto_instance base;
+		} s;
+		struct akcipher_alg alg;
+	};
+};
+
+struct crypto_akcipher_spawn {
+	struct crypto_spawn base;
+};
+
+/*
+ * Transform internal helpers.
+ */
+static inline void *akcipher_request_ctx(struct akcipher_request *req)
+{
+	return req->__ctx;
+}
+
+static inline void *akcipher_request_ctx_dma(struct akcipher_request *req)
+{
+	unsigned int align = crypto_dma_align();
+
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+
+	return PTR_ALIGN(akcipher_request_ctx(req), align);
+}
+
+static inline void akcipher_set_reqsize(struct crypto_akcipher *akcipher,
+					unsigned int reqsize)
+{
+	akcipher->reqsize = reqsize;
+}
+
+static inline void akcipher_set_reqsize_dma(struct crypto_akcipher *akcipher,
+					    unsigned int reqsize)
+{
+	reqsize += crypto_dma_align() & ~(crypto_tfm_ctx_alignment() - 1);
+	akcipher->reqsize = reqsize;
+}
+
+static inline void *akcipher_tfm_ctx(struct crypto_akcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *akcipher_tfm_ctx_dma(struct crypto_akcipher *tfm)
+{
+	return crypto_tfm_ctx_dma(&tfm->base);
+}
+
+static inline void akcipher_request_complete(struct akcipher_request *req,
+					     int err)
+{
+	crypto_request_complete(&req->base, err);
+}
+
+static inline const char *akcipher_alg_name(struct crypto_akcipher *tfm)
+{
+	return crypto_akcipher_tfm(tfm)->__crt_alg->cra_name;
+}
+
+static inline struct crypto_instance *akcipher_crypto_instance(
+		struct akcipher_instance *inst)
+{
+	return container_of(&inst->alg.base, struct crypto_instance, alg);
+}
+
+static inline struct akcipher_instance *akcipher_instance(
+		struct crypto_instance *inst)
+{
+	return container_of(&inst->alg, struct akcipher_instance, alg.base);
+}
+
+static inline struct akcipher_instance *akcipher_alg_instance(
+		struct crypto_akcipher *akcipher)
+{
+	return akcipher_instance(crypto_tfm_alg_instance(&akcipher->base));
+}
+
+static inline void *akcipher_instance_ctx(struct akcipher_instance *inst)
+{
+	return crypto_instance_ctx(akcipher_crypto_instance(inst));
+}
+
+int crypto_grab_akcipher(struct crypto_akcipher_spawn *spawn,
+			 struct crypto_instance *inst,
+			 const char *name, u32 type, u32 mask);
+
+static inline struct crypto_akcipher *crypto_spawn_akcipher(
+		struct crypto_akcipher_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+static inline void crypto_drop_akcipher(struct crypto_akcipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline struct akcipher_alg *crypto_spawn_akcipher_alg(
+		struct crypto_akcipher_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct akcipher_alg, base);
+}
+
+/**
+ * crypto_register_akcipher() -- Register public key algorithm
+ *
+ * Function registers an implementation of a public key cipher algorithm
+ *
+ * @alg:	algorithm definition
+ *
+ * Return: zero on success; error code in case of error
+ */
+int crypto_register_akcipher(struct akcipher_alg *alg);
+
+/**
+ * crypto_unregister_akcipher() -- Unregister public key algorithm
+ *
+ * Function unregisters an implementation of a public key cipher algorithm
+ *
+ * @alg:	algorithm definition
+ */
+void crypto_unregister_akcipher(struct akcipher_alg *alg);
+
+/**
+ * akcipher_register_instance() -- Unregister public key template instance
+ *
+ * Function registers an implementation of an asymmetric key algorithm
+ * created from a template
+ *
+ * @tmpl:	the template from which the algorithm was created
+ * @inst:	the template instance
+ */
+int akcipher_register_instance(struct crypto_template *tmpl,
+		struct akcipher_instance *inst);
+#endif