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, 160 insertions, 0 deletions

diff --git a/include/crypto/blake2s.h b/include/crypto/blake2s.h
new file mode 100644
index 000000000..648cb7824
--- /dev/null
+++ b/include/crypto/blake2s.h
@@ -0,0 +1,160 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef _CRYPTO_BLAKE2S_H
+#define _CRYPTO_BLAKE2S_H
+
+#include <linux/bug.h>
+#include <linux/kconfig.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+enum blake2s_lengths {
+	BLAKE2S_BLOCK_SIZE = 64,
+	BLAKE2S_HASH_SIZE = 32,
+	BLAKE2S_KEY_SIZE = 32,
+
+	BLAKE2S_128_HASH_SIZE = 16,
+	BLAKE2S_160_HASH_SIZE = 20,
+	BLAKE2S_224_HASH_SIZE = 28,
+	BLAKE2S_256_HASH_SIZE = 32,
+};
+
+/**
+ * struct blake2s_ctx - Context for hashing a message with BLAKE2s
+ * @h: compression function state
+ * @t: block counter
+ * @f: finalization indicator
+ * @buf: partial block buffer; 'buflen' bytes are valid
+ * @buflen: number of bytes buffered in @buf
+ * @outlen: length of output hash value in bytes, at most BLAKE2S_HASH_SIZE
+ */
+struct blake2s_ctx {
+	/* 'h', 't', and 'f' are used in assembly code, so keep them as-is. */
+	u32 h[8];
+	u32 t[2];
+	u32 f[2];
+	u8 buf[BLAKE2S_BLOCK_SIZE];
+	unsigned int buflen;
+	unsigned int outlen;
+};
+
+enum blake2s_iv {
+	BLAKE2S_IV0 = 0x6A09E667UL,
+	BLAKE2S_IV1 = 0xBB67AE85UL,
+	BLAKE2S_IV2 = 0x3C6EF372UL,
+	BLAKE2S_IV3 = 0xA54FF53AUL,
+	BLAKE2S_IV4 = 0x510E527FUL,
+	BLAKE2S_IV5 = 0x9B05688CUL,
+	BLAKE2S_IV6 = 0x1F83D9ABUL,
+	BLAKE2S_IV7 = 0x5BE0CD19UL,
+};
+
+static inline void __blake2s_init(struct blake2s_ctx *ctx, size_t outlen,
+				  const void *key, size_t keylen)
+{
+	ctx->h[0] = BLAKE2S_IV0 ^ (0x01010000 | keylen << 8 | outlen);
+	ctx->h[1] = BLAKE2S_IV1;
+	ctx->h[2] = BLAKE2S_IV2;
+	ctx->h[3] = BLAKE2S_IV3;
+	ctx->h[4] = BLAKE2S_IV4;
+	ctx->h[5] = BLAKE2S_IV5;
+	ctx->h[6] = BLAKE2S_IV6;
+	ctx->h[7] = BLAKE2S_IV7;
+	ctx->t[0] = 0;
+	ctx->t[1] = 0;
+	ctx->f[0] = 0;
+	ctx->f[1] = 0;
+	ctx->buflen = 0;
+	ctx->outlen = outlen;
+	if (keylen) {
+		memcpy(ctx->buf, key, keylen);
+		memset(&ctx->buf[keylen], 0, BLAKE2S_BLOCK_SIZE - keylen);
+		ctx->buflen = BLAKE2S_BLOCK_SIZE;
+	}
+}
+
+/**
+ * blake2s_init() - Initialize a BLAKE2s context for a new message (unkeyed)
+ * @ctx: the context to initialize
+ * @outlen: length of output hash value in bytes, at most BLAKE2S_HASH_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2s_init(struct blake2s_ctx *ctx, size_t outlen)
+{
+	__blake2s_init(ctx, outlen, NULL, 0);
+}
+
+/**
+ * blake2s_init_key() - Initialize a BLAKE2s context for a new message (keyed)
+ * @ctx: the context to initialize
+ * @outlen: length of output hash value in bytes, at most BLAKE2S_HASH_SIZE
+ * @key: the key
+ * @keylen: the key length in bytes, at most BLAKE2S_KEY_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2s_init_key(struct blake2s_ctx *ctx, size_t outlen,
+				    const void *key, size_t keylen)
+{
+	WARN_ON(IS_ENABLED(DEBUG) && (!outlen || outlen > BLAKE2S_HASH_SIZE ||
+		!key || !keylen || keylen > BLAKE2S_KEY_SIZE));
+
+	__blake2s_init(ctx, outlen, key, keylen);
+}
+
+/**
+ * blake2s_update() - Update a BLAKE2s context with message data
+ * @ctx: the context to update; must have been initialized
+ * @in: the message data
+ * @inlen: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void blake2s_update(struct blake2s_ctx *ctx, const u8 *in, size_t inlen);
+
+/**
+ * blake2s_final() - Finish computing a BLAKE2s hash
+ * @ctx: the context to finalize; must have been initialized
+ * @out: (output) the resulting BLAKE2s hash.  Its length will be equal to the
+ *	 @outlen that was passed to blake2s_init() or blake2s_init_key().
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void blake2s_final(struct blake2s_ctx *ctx, u8 *out);
+
+/**
+ * blake2s() - Compute BLAKE2s hash in one shot
+ * @key: the key, or NULL for an unkeyed hash
+ * @keylen: the key length in bytes (at most BLAKE2S_KEY_SIZE), or 0 for an
+ *	    unkeyed hash
+ * @in: the message data
+ * @inlen: the data length in bytes
+ * @out: (output) the resulting BLAKE2s hash, with length @outlen
+ * @outlen: length of output hash value in bytes, at most BLAKE2S_HASH_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2s(const u8 *key, size_t keylen,
+			   const u8 *in, size_t inlen,
+			   u8 *out, size_t outlen)
+{
+	struct blake2s_ctx ctx;
+
+	WARN_ON(IS_ENABLED(DEBUG) && ((!in && inlen > 0) || !out || !outlen ||
+		outlen > BLAKE2S_HASH_SIZE || keylen > BLAKE2S_KEY_SIZE ||
+		(!key && keylen)));
+
+	__blake2s_init(&ctx, outlen, key, keylen);
+	blake2s_update(&ctx, in, inlen);
+	blake2s_final(&ctx, out);
+}
+
+#endif /* _CRYPTO_BLAKE2S_H */