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, 87 insertions, 0 deletions

diff --git a/include/crypto/sm3.h b/include/crypto/sm3.h
new file mode 100644
index 000000000..371e8a661
--- /dev/null
+++ b/include/crypto/sm3.h
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * SM3 hash algorithm
+ *
+ * Copyright (C) 2017 ARM Limited or its affiliates.
+ * Copyright (C) 2017 Gilad Ben-Yossef <gilad@benyossef.com>
+ * Copyright (C) 2021 Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
+ */
+
+#ifndef _CRYPTO_SM3_H
+#define _CRYPTO_SM3_H
+
+#include <linux/types.h>
+
+#define SM3_DIGEST_SIZE	32
+#define SM3_BLOCK_SIZE	64
+
+#define SM3_IVA		0x7380166f
+#define SM3_IVB		0x4914b2b9
+#define SM3_IVC		0x172442d7
+#define SM3_IVD		0xda8a0600
+#define SM3_IVE		0xa96f30bc
+#define SM3_IVF		0x163138aa
+#define SM3_IVG		0xe38dee4d
+#define SM3_IVH		0xb0fb0e4e
+
+/* State for the SM3 compression function */
+struct sm3_block_state {
+	u32 h[SM3_DIGEST_SIZE / 4];
+};
+
+/**
+ * struct sm3_ctx - Context for hashing a message with SM3
+ * @state: the compression function state
+ * @bytecount: number of bytes processed so far
+ * @buf: partial block buffer; bytecount % SM3_BLOCK_SIZE bytes are valid
+ */
+struct sm3_ctx {
+	struct sm3_block_state state;
+	u64 bytecount;
+	u8 buf[SM3_BLOCK_SIZE] __aligned(__alignof__(__be64));
+};
+
+/**
+ * sm3_init() - Initialize an SM3 context for a new message
+ * @ctx: the context to initialize
+ *
+ * If you don't need incremental computation, consider sm3() instead.
+ *
+ * Context: Any context.
+ */
+void sm3_init(struct sm3_ctx *ctx);
+
+/**
+ * sm3_update() - Update an SM3 context with message data
+ * @ctx: the context to update; must have been initialized
+ * @data: the message data
+ * @len: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void sm3_update(struct sm3_ctx *ctx, const u8 *data, size_t len);
+
+/**
+ * sm3_final() - Finish computing an SM3 message digest
+ * @ctx: the context to finalize; must have been initialized
+ * @out: (output) the resulting SM3 message digest
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void sm3_final(struct sm3_ctx *ctx, u8 out[at_least SM3_DIGEST_SIZE]);
+
+/**
+ * sm3() - Compute SM3 message digest in one shot
+ * @data: the message data
+ * @len: the data length in bytes
+ * @out: (output) the resulting SM3 message digest
+ *
+ * Context: Any context.
+ */
+void sm3(const u8 *data, size_t len, u8 out[at_least SM3_DIGEST_SIZE]);
+
+#endif /* _CRYPTO_SM3_H */