openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/tools/perf/util/blake2s.h b/tools/perf/util/blake2s.h
new file mode 100644
index 000000000..a1fe81a4b
--- /dev/null
+++ b/tools/perf/util/blake2s.h
@@ -0,0 +1,73 @@
+/* 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 <string.h>
+#include <linux/types.h>
+
+#define BLAKE2S_BLOCK_SIZE 64
+
+struct blake2s_ctx {
+	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;
+	}
+}
+
+static inline void blake2s_init(struct blake2s_ctx *ctx, size_t outlen)
+{
+	__blake2s_init(ctx, outlen, NULL, 0);
+}
+
+static inline void blake2s_init_key(struct blake2s_ctx *ctx, size_t outlen,
+				    const void *key, size_t keylen)
+{
+	__blake2s_init(ctx, outlen, key, keylen);
+}
+
+void blake2s_update(struct blake2s_ctx *ctx, const u8 *in, size_t inlen);
+
+void blake2s_final(struct blake2s_ctx *ctx, u8 *out);
+
+#endif /* _CRYPTO_BLAKE2S_H */