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, 27 insertions, 0 deletions

diff --git a/lib/debug_info.c b/lib/debug_info.c
new file mode 100644
index 000000000..cc4723c74
--- /dev/null
+++ b/lib/debug_info.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file exists solely to ensure debug information for some core
+ * data structures is included in the final image even for
+ * CONFIG_DEBUG_INFO_REDUCED. Please do not add actual code. However,
+ * adding appropriate #includes is fine.
+ */
+#include <linux/cred.h>
+#include <linux/crypto.h>
+#include <linux/dcache.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/fscache-cache.h>
+#include <linux/io.h>
+#include <linux/kallsyms.h>
+#include <linux/kernel.h>
+#include <linux/kobject.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/stdarg.h>
+#include <linux/types.h>
+#include <net/addrconf.h>
+#include <net/sock.h>
+#include <net/tcp.h>