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, 45 insertions, 0 deletions

diff --git a/fs/lockd/netlink.c b/fs/lockd/netlink.c
new file mode 100644
index 000000000..880c42b4f
--- /dev/null
+++ b/fs/lockd/netlink.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/lockd.yaml */
+/* YNL-GEN kernel source */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "netlink.h"
+
+#include <uapi/linux/lockd_netlink.h>
+
+/* LOCKD_CMD_SERVER_SET - do */
+static const struct nla_policy lockd_server_set_nl_policy[LOCKD_A_SERVER_UDP_PORT + 1] = {
+	[LOCKD_A_SERVER_GRACETIME] = { .type = NLA_U32, },
+	[LOCKD_A_SERVER_TCP_PORT] = { .type = NLA_U16, },
+	[LOCKD_A_SERVER_UDP_PORT] = { .type = NLA_U16, },
+};
+
+/* Ops table for lockd */
+static const struct genl_split_ops lockd_nl_ops[] = {
+	{
+		.cmd		= LOCKD_CMD_SERVER_SET,
+		.doit		= lockd_nl_server_set_doit,
+		.policy		= lockd_server_set_nl_policy,
+		.maxattr	= LOCKD_A_SERVER_UDP_PORT,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd	= LOCKD_CMD_SERVER_GET,
+		.doit	= lockd_nl_server_get_doit,
+		.flags	= GENL_CMD_CAP_DO,
+	},
+};
+
+struct genl_family lockd_nl_family __ro_after_init = {
+	.name		= LOCKD_FAMILY_NAME,
+	.version	= LOCKD_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= lockd_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(lockd_nl_ops),
+};