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, 92 insertions, 0 deletions

diff --git a/include/uapi/mtd/inftl-user.h b/include/uapi/mtd/inftl-user.h
new file mode 100644
index 000000000..8d5044e32
--- /dev/null
+++ b/include/uapi/mtd/inftl-user.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Parts of INFTL headers shared with userspace
+ *
+ */
+
+#ifndef __MTD_INFTL_USER_H__
+#define __MTD_INFTL_USER_H__
+
+#include <linux/types.h>
+
+#define	OSAK_VERSION	0x5120
+#define	PERCENTUSED	98
+
+#define	SECTORSIZE	512
+
+/* Block Control Information */
+
+struct inftl_bci {
+	__u8 ECCsig[6];
+	__u8 Status;
+	__u8 Status1;
+} __attribute__((packed));
+
+struct inftl_unithead1 {
+	__u16 virtualUnitNo;
+	__u16 prevUnitNo;
+	__u8 ANAC;
+	__u8 NACs;
+	__u8 parityPerField;
+	__u8 discarded;
+} __attribute__((packed));
+
+struct inftl_unithead2 {
+	__u8 parityPerField;
+	__u8 ANAC;
+	__u16 prevUnitNo;
+	__u16 virtualUnitNo;
+	__u8 NACs;
+	__u8 discarded;
+} __attribute__((packed));
+
+struct inftl_unittail {
+	__u8 Reserved[4];
+	__u16 EraseMark;
+	__u16 EraseMark1;
+} __attribute__((packed));
+
+union inftl_uci {
+	struct inftl_unithead1 a;
+	struct inftl_unithead2 b;
+	struct inftl_unittail c;
+};
+
+struct inftl_oob {
+	struct inftl_bci b;
+	union inftl_uci u;
+};
+
+
+/* INFTL Media Header */
+
+struct INFTLPartition {
+	__u32 virtualUnits;
+	__u32 firstUnit;
+	__u32 lastUnit;
+	__u32 flags;
+	__u32 spareUnits;
+	__u32 Reserved0;
+	__u32 Reserved1;
+} __attribute__((packed));
+
+struct INFTLMediaHeader {
+	char bootRecordID[8];
+	__u32 NoOfBootImageBlocks;
+	__u32 NoOfBinaryPartitions;
+	__u32 NoOfBDTLPartitions;
+	__u32 BlockMultiplierBits;
+	__u32 FormatFlags;
+	__u32 OsakVersion;
+	__u32 PercentUsed;
+	struct INFTLPartition Partitions[4];
+} __attribute__((packed));
+
+/* Partition flag types */
+#define	INFTL_BINARY	0x20000000
+#define	INFTL_BDTL	0x40000000
+#define	INFTL_LAST	0x80000000
+
+#endif /* __MTD_INFTL_USER_H__ */
+
+