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, 49 insertions, 0 deletions

diff --git a/net/ipv4/fou_nl.c b/net/ipv4/fou_nl.c
new file mode 100644
index 000000000..309d5ba98
--- /dev/null
+++ b/net/ipv4/fou_nl.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/fou.yaml */
+/* YNL-GEN kernel source */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "fou_nl.h"
+
+#include <uapi/linux/fou.h>
+
+/* Global operation policy for fou */
+const struct nla_policy fou_nl_policy[FOU_ATTR_IFINDEX + 1] = {
+	[FOU_ATTR_PORT] = { .type = NLA_BE16, },
+	[FOU_ATTR_AF] = { .type = NLA_U8, },
+	[FOU_ATTR_IPPROTO] = NLA_POLICY_MIN(NLA_U8, 1),
+	[FOU_ATTR_TYPE] = { .type = NLA_U8, },
+	[FOU_ATTR_REMCSUM_NOPARTIAL] = { .type = NLA_FLAG, },
+	[FOU_ATTR_LOCAL_V4] = { .type = NLA_U32, },
+	[FOU_ATTR_LOCAL_V6] = NLA_POLICY_EXACT_LEN(16),
+	[FOU_ATTR_PEER_V4] = { .type = NLA_U32, },
+	[FOU_ATTR_PEER_V6] = NLA_POLICY_EXACT_LEN(16),
+	[FOU_ATTR_PEER_PORT] = { .type = NLA_BE16, },
+	[FOU_ATTR_IFINDEX] = { .type = NLA_S32, },
+};
+
+/* Ops table for fou */
+const struct genl_small_ops fou_nl_ops[3] = {
+	{
+		.cmd		= FOU_CMD_ADD,
+		.validate	= GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit		= fou_nl_add_doit,
+		.flags		= GENL_ADMIN_PERM,
+	},
+	{
+		.cmd		= FOU_CMD_DEL,
+		.validate	= GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit		= fou_nl_del_doit,
+		.flags		= GENL_ADMIN_PERM,
+	},
+	{
+		.cmd		= FOU_CMD_GET,
+		.validate	= GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit		= fou_nl_get_doit,
+		.dumpit		= fou_nl_get_dumpit,
+	},
+};