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, 30 insertions, 0 deletions

diff --git a/crypto/ripemd.h b/crypto/ripemd.h
new file mode 100644
index 000000000..b977785e2
--- /dev/null
+++ b/crypto/ripemd.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values for RIPEMD algorithms
+ */
+
+#ifndef _CRYPTO_RMD_H
+#define _CRYPTO_RMD_H
+
+#define RMD160_DIGEST_SIZE      20
+#define RMD160_BLOCK_SIZE       64
+
+/* initial values  */
+#define RMD_H0  0x67452301UL
+#define RMD_H1  0xefcdab89UL
+#define RMD_H2  0x98badcfeUL
+#define RMD_H3  0x10325476UL
+#define RMD_H4  0xc3d2e1f0UL
+
+/* constants */
+#define RMD_K1  0x00000000UL
+#define RMD_K2  0x5a827999UL
+#define RMD_K3  0x6ed9eba1UL
+#define RMD_K4  0x8f1bbcdcUL
+#define RMD_K5  0xa953fd4eUL
+#define RMD_K6  0x50a28be6UL
+#define RMD_K7  0x5c4dd124UL
+#define RMD_K8  0x6d703ef3UL
+#define RMD_K9  0x7a6d76e9UL
+
+#endif