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, 56 insertions, 0 deletions

diff --git a/fs/lockd/nlm.h b/fs/lockd/nlm.h
new file mode 100644
index 000000000..47be65d01
--- /dev/null
+++ b/fs/lockd/nlm.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Declarations for the Network Lock Manager protocol.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#ifndef _LOCKD_NLM_H
+#define _LOCKD_NLM_H
+
+
+/* Maximum file offset in file_lock.fl_end */
+# define NLM_OFFSET_MAX		((s32) 0x7fffffff)
+# define NLM4_OFFSET_MAX	((s64) ((~(u64)0) >> 1))
+
+/* Return states for NLM */
+enum {
+	NLM_LCK_GRANTED			= 0,
+	NLM_LCK_DENIED			= 1,
+	NLM_LCK_DENIED_NOLOCKS		= 2,
+	NLM_LCK_BLOCKED			= 3,
+	NLM_LCK_DENIED_GRACE_PERIOD	= 4,
+#ifdef CONFIG_LOCKD_V4
+	NLM_DEADLCK			= 5,
+	NLM_ROFS			= 6,
+	NLM_STALE_FH			= 7,
+	NLM_FBIG			= 8,
+	NLM_FAILED			= 9,
+#endif
+};
+
+#define NLM_PROGRAM		100021
+
+#define NLMPROC_NULL		0
+#define NLMPROC_TEST		1
+#define NLMPROC_LOCK		2
+#define NLMPROC_CANCEL		3
+#define NLMPROC_UNLOCK		4
+#define NLMPROC_GRANTED		5
+#define NLMPROC_TEST_MSG	6
+#define NLMPROC_LOCK_MSG	7
+#define NLMPROC_CANCEL_MSG	8
+#define NLMPROC_UNLOCK_MSG	9
+#define NLMPROC_GRANTED_MSG	10
+#define NLMPROC_TEST_RES	11
+#define NLMPROC_LOCK_RES	12
+#define NLMPROC_CANCEL_RES	13
+#define NLMPROC_UNLOCK_RES	14
+#define NLMPROC_GRANTED_RES	15
+#define NLMPROC_NSM_NOTIFY	16		/* statd callback */
+#define NLMPROC_SHARE		20
+#define NLMPROC_UNSHARE		21
+#define NLMPROC_NM_LOCK		22
+#define NLMPROC_FREE_ALL	23
+
+#endif /* _LOCKD_NLM_H */