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, 106 insertions, 0 deletions

diff --git a/crypto/xxhash_generic.c b/crypto/xxhash_generic.c
new file mode 100644
index 000000000..175bb7ae0
--- /dev/null
+++ b/crypto/xxhash_generic.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <crypto/internal/hash.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/xxhash.h>
+#include <linux/unaligned.h>
+
+#define XXHASH64_BLOCK_SIZE	32
+#define XXHASH64_DIGEST_SIZE	8
+
+struct xxhash64_tfm_ctx {
+	u64 seed;
+};
+
+struct xxhash64_desc_ctx {
+	struct xxh64_state xxhstate;
+};
+
+static int xxhash64_setkey(struct crypto_shash *tfm, const u8 *key,
+			 unsigned int keylen)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(tfm);
+
+	if (keylen != sizeof(tctx->seed))
+		return -EINVAL;
+	tctx->seed = get_unaligned_le64(key);
+	return 0;
+}
+
+static int xxhash64_init(struct shash_desc *desc)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	xxh64_reset(&dctx->xxhstate, tctx->seed);
+
+	return 0;
+}
+
+static int xxhash64_update(struct shash_desc *desc, const u8 *data,
+			 unsigned int length)
+{
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	xxh64_update(&dctx->xxhstate, data, length);
+
+	return 0;
+}
+
+static int xxhash64_final(struct shash_desc *desc, u8 *out)
+{
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	put_unaligned_le64(xxh64_digest(&dctx->xxhstate), out);
+
+	return 0;
+}
+
+static int xxhash64_digest(struct shash_desc *desc, const u8 *data,
+			 unsigned int length, u8 *out)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
+
+	put_unaligned_le64(xxh64(data, length, tctx->seed), out);
+
+	return 0;
+}
+
+static struct shash_alg alg = {
+	.digestsize	= XXHASH64_DIGEST_SIZE,
+	.setkey		= xxhash64_setkey,
+	.init		= xxhash64_init,
+	.update		= xxhash64_update,
+	.final		= xxhash64_final,
+	.digest		= xxhash64_digest,
+	.descsize	= sizeof(struct xxhash64_desc_ctx),
+	.base		= {
+		.cra_name	 = "xxhash64",
+		.cra_driver_name = "xxhash64-generic",
+		.cra_priority	 = 100,
+		.cra_flags	 = CRYPTO_ALG_OPTIONAL_KEY,
+		.cra_blocksize	 = XXHASH64_BLOCK_SIZE,
+		.cra_ctxsize	 = sizeof(struct xxhash64_tfm_ctx),
+		.cra_module	 = THIS_MODULE,
+	}
+};
+
+static int __init xxhash_mod_init(void)
+{
+	return crypto_register_shash(&alg);
+}
+
+static void __exit xxhash_mod_fini(void)
+{
+	crypto_unregister_shash(&alg);
+}
+
+module_init(xxhash_mod_init);
+module_exit(xxhash_mod_fini);
+
+MODULE_AUTHOR("Nikolay Borisov <nborisov@suse.com>");
+MODULE_DESCRIPTION("xxhash calculations wrapper for lib/xxhash.c");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_CRYPTO("xxhash64");
+MODULE_ALIAS_CRYPTO("xxhash64-generic");