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, 100 insertions, 0 deletions

diff --git a/lib/crypto/poly1305.c b/lib/crypto/poly1305.c
new file mode 100644
index 000000000..f313ccc4b
--- /dev/null
+++ b/lib/crypto/poly1305.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Poly1305 authenticator algorithm, RFC7539
+ *
+ * Copyright (C) 2015 Martin Willi
+ *
+ * Based on public domain code by Andrew Moon and Daniel J. Bernstein.
+ */
+
+#include <crypto/internal/poly1305.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/unaligned.h>
+
+#ifdef CONFIG_CRYPTO_LIB_POLY1305_ARCH
+#include "poly1305.h" /* $(SRCARCH)/poly1305.h */
+#else
+#define poly1305_block_init	poly1305_block_init_generic
+#define poly1305_blocks		poly1305_blocks_generic
+#define poly1305_emit		poly1305_emit_generic
+#endif
+
+void poly1305_init(struct poly1305_desc_ctx *desc,
+		   const u8 key[POLY1305_KEY_SIZE])
+{
+	desc->s[0] = get_unaligned_le32(key + 16);
+	desc->s[1] = get_unaligned_le32(key + 20);
+	desc->s[2] = get_unaligned_le32(key + 24);
+	desc->s[3] = get_unaligned_le32(key + 28);
+	desc->buflen = 0;
+	poly1305_block_init(&desc->state, key);
+}
+EXPORT_SYMBOL(poly1305_init);
+
+void poly1305_update(struct poly1305_desc_ctx *desc,
+		     const u8 *src, unsigned int nbytes)
+{
+	if (desc->buflen + nbytes >= POLY1305_BLOCK_SIZE) {
+		unsigned int bulk_len;
+
+		if (desc->buflen) {
+			unsigned int l = POLY1305_BLOCK_SIZE - desc->buflen;
+
+			memcpy(&desc->buf[desc->buflen], src, l);
+			src += l;
+			nbytes -= l;
+
+			poly1305_blocks(&desc->state, desc->buf,
+					POLY1305_BLOCK_SIZE, 1);
+			desc->buflen = 0;
+		}
+
+		bulk_len = round_down(nbytes, POLY1305_BLOCK_SIZE);
+		nbytes %= POLY1305_BLOCK_SIZE;
+
+		if (bulk_len) {
+			poly1305_blocks(&desc->state, src, bulk_len, 1);
+			src += bulk_len;
+		}
+	}
+	if (nbytes) {
+		memcpy(&desc->buf[desc->buflen], src, nbytes);
+		desc->buflen += nbytes;
+	}
+}
+EXPORT_SYMBOL(poly1305_update);
+
+void poly1305_final(struct poly1305_desc_ctx *desc, u8 *dst)
+{
+	if (unlikely(desc->buflen)) {
+		desc->buf[desc->buflen++] = 1;
+		memset(desc->buf + desc->buflen, 0,
+		       POLY1305_BLOCK_SIZE - desc->buflen);
+		poly1305_blocks(&desc->state, desc->buf, POLY1305_BLOCK_SIZE,
+				0);
+	}
+
+	poly1305_emit(&desc->state.h, dst, desc->s);
+	*desc = (struct poly1305_desc_ctx){};
+}
+EXPORT_SYMBOL(poly1305_final);
+
+#ifdef poly1305_mod_init_arch
+static int __init poly1305_mod_init(void)
+{
+	poly1305_mod_init_arch();
+	return 0;
+}
+subsys_initcall(poly1305_mod_init);
+
+static void __exit poly1305_mod_exit(void)
+{
+}
+module_exit(poly1305_mod_exit);
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Poly1305 authenticator algorithm, RFC7539");