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, 24 insertions, 0 deletions

diff --git a/include/crypto/cast5.h b/include/crypto/cast5.h
new file mode 100644
index 000000000..3d4ed4ea9
--- /dev/null
+++ b/include/crypto/cast5.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _CRYPTO_CAST5_H
+#define _CRYPTO_CAST5_H
+
+#include <linux/types.h>
+#include <linux/crypto.h>
+#include <crypto/cast_common.h>
+
+#define CAST5_BLOCK_SIZE 8
+#define CAST5_MIN_KEY_SIZE 5
+#define CAST5_MAX_KEY_SIZE 16
+
+struct cast5_ctx {
+	u32 Km[16];
+	u8 Kr[16];
+	int rr;	/* rr ? rounds = 12 : rounds = 16; (rfc 2144) */
+};
+
+int cast5_setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen);
+
+void __cast5_encrypt(struct cast5_ctx *ctx, u8 *dst, const u8 *src);
+void __cast5_decrypt(struct cast5_ctx *ctx, u8 *dst, const u8 *src);
+
+#endif