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, 99 insertions, 0 deletions

diff --git a/crypto/lz4.c b/crypto/lz4.c
new file mode 100644
index 000000000..57b713516
--- /dev/null
+++ b/crypto/lz4.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Cryptographic API.
+ *
+ * Copyright (c) 2013 Chanho Min <chanho.min@lge.com>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/vmalloc.h>
+#include <linux/lz4.h>
+#include <crypto/internal/scompress.h>
+
+static void *lz4_alloc_ctx(void)
+{
+	void *ctx;
+
+	ctx = vmalloc(LZ4_MEM_COMPRESS);
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	return ctx;
+}
+
+static void lz4_free_ctx(void *ctx)
+{
+	vfree(ctx);
+}
+
+static int __lz4_compress_crypto(const u8 *src, unsigned int slen,
+				 u8 *dst, unsigned int *dlen, void *ctx)
+{
+	int out_len = LZ4_compress_default(src, dst,
+		slen, *dlen, ctx);
+
+	if (!out_len)
+		return -EINVAL;
+
+	*dlen = out_len;
+	return 0;
+}
+
+static int lz4_scompress(struct crypto_scomp *tfm, const u8 *src,
+			 unsigned int slen, u8 *dst, unsigned int *dlen,
+			 void *ctx)
+{
+	return __lz4_compress_crypto(src, slen, dst, dlen, ctx);
+}
+
+static int __lz4_decompress_crypto(const u8 *src, unsigned int slen,
+				   u8 *dst, unsigned int *dlen, void *ctx)
+{
+	int out_len = LZ4_decompress_safe(src, dst, slen, *dlen);
+
+	if (out_len < 0)
+		return -EINVAL;
+
+	*dlen = out_len;
+	return 0;
+}
+
+static int lz4_sdecompress(struct crypto_scomp *tfm, const u8 *src,
+			   unsigned int slen, u8 *dst, unsigned int *dlen,
+			   void *ctx)
+{
+	return __lz4_decompress_crypto(src, slen, dst, dlen, NULL);
+}
+
+static struct scomp_alg scomp = {
+	.streams		= {
+		.alloc_ctx	= lz4_alloc_ctx,
+		.free_ctx	= lz4_free_ctx,
+	},
+	.compress		= lz4_scompress,
+	.decompress		= lz4_sdecompress,
+	.base			= {
+		.cra_name	= "lz4",
+		.cra_driver_name = "lz4-scomp",
+		.cra_module	 = THIS_MODULE,
+	}
+};
+
+static int __init lz4_mod_init(void)
+{
+	return crypto_register_scomp(&scomp);
+}
+
+static void __exit lz4_mod_fini(void)
+{
+	crypto_unregister_scomp(&scomp);
+}
+
+module_init(lz4_mod_init);
+module_exit(lz4_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("LZ4 Compression Algorithm");
+MODULE_ALIAS_CRYPTO("lz4");