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, 103 insertions, 0 deletions

diff --git a/crypto/proc.c b/crypto/proc.c
new file mode 100644
index 000000000..5fb9fe86d
--- /dev/null
+++ b/crypto/proc.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Scatterlist Cryptographic API.
+ *
+ * Procfs information.
+ *
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ * Copyright (c) 2005 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/atomic.h>
+#include <linux/init.h>
+#include <linux/crypto.h>
+#include <linux/fips.h>
+#include <linux/module.h>	/* for module_name() */
+#include <linux/rwsem.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+	__acquires_shared(&crypto_alg_sem)
+{
+	down_read(&crypto_alg_sem);
+	return seq_list_start(&crypto_alg_list, *pos);
+}
+
+static void *c_next(struct seq_file *m, void *p, loff_t *pos)
+	__must_hold_shared(&crypto_alg_sem)
+{
+	return seq_list_next(p, &crypto_alg_list, pos);
+}
+
+static void c_stop(struct seq_file *m, void *p)
+	__releases_shared(&crypto_alg_sem)
+{
+	up_read(&crypto_alg_sem);
+}
+
+static int c_show(struct seq_file *m, void *p)
+{
+	struct crypto_alg *alg = list_entry(p, struct crypto_alg, cra_list);
+
+	seq_printf(m, "name         : %s\n", alg->cra_name);
+	seq_printf(m, "driver       : %s\n", alg->cra_driver_name);
+	seq_printf(m, "module       : %s\n", module_name(alg->cra_module));
+	seq_printf(m, "priority     : %d\n", alg->cra_priority);
+	seq_printf(m, "refcnt       : %u\n", refcount_read(&alg->cra_refcnt));
+	seq_printf(m, "selftest     : %s\n",
+		   (alg->cra_flags & CRYPTO_ALG_TESTED) ?
+		   "passed" : "unknown");
+	seq_printf(m, "internal     : %s\n",
+		   str_yes_no(alg->cra_flags & CRYPTO_ALG_INTERNAL));
+	if (fips_enabled)
+		seq_printf(m, "fips         : %s\n",
+			str_no_yes(alg->cra_flags & CRYPTO_ALG_FIPS_INTERNAL));
+
+	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
+		seq_printf(m, "type         : larval\n");
+		seq_printf(m, "flags        : 0x%x\n", alg->cra_flags);
+		goto out;
+	}
+
+	if (alg->cra_type && alg->cra_type->show) {
+		alg->cra_type->show(m, alg);
+		goto out;
+	}
+
+	switch (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) {
+	case CRYPTO_ALG_TYPE_CIPHER:
+		seq_printf(m, "type         : cipher\n");
+		seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
+		seq_printf(m, "min keysize  : %u\n",
+					alg->cra_cipher.cia_min_keysize);
+		seq_printf(m, "max keysize  : %u\n",
+					alg->cra_cipher.cia_max_keysize);
+		break;
+	default:
+		seq_printf(m, "type         : unknown\n");
+		break;
+	}
+
+out:
+	seq_putc(m, '\n');
+	return 0;
+}
+
+static const struct seq_operations crypto_seq_ops = {
+	.start		= c_start,
+	.next		= c_next,
+	.stop		= c_stop,
+	.show		= c_show
+};
+
+void __init crypto_init_proc(void)
+{
+	proc_create_seq("crypto", 0, NULL, &crypto_seq_ops);
+}
+
+void __exit crypto_exit_proc(void)
+{
+	remove_proc_entry("crypto", NULL);
+}