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, 15 insertions, 0 deletions

diff --git a/fs/afs/protocol_afs.h b/fs/afs/protocol_afs.h
new file mode 100644
index 000000000..0c39358c8
--- /dev/null
+++ b/fs/afs/protocol_afs.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* AFS protocol bits
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+
+#define AFSCAPABILITIESMAX 196 /* Maximum number of words in a capability set */
+
+/* AFS3 Fileserver capabilities word 0 */
+#define AFS3_VICED_CAPABILITY_ERRORTRANS	0x0001 /* Uses UAE errors */
+#define AFS3_VICED_CAPABILITY_64BITFILES	0x0002 /* FetchData64 & StoreData64 supported */
+#define AFS3_VICED_CAPABILITY_WRITELOCKACL	0x0004 /* Can lock a file even without lock perm */
+#define AFS3_VICED_CAPABILITY_SANEACLS		0x0008 /* ACLs reviewed for sanity - don't use */