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, 46 insertions, 0 deletions

diff --git a/include/net/ax88796.h b/include/net/ax88796.h
new file mode 100644
index 000000000..303100f08
--- /dev/null
+++ b/include/net/ax88796.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* include/net/ax88796.h
+ *
+ * Copyright 2005 Simtec Electronics
+ *	Ben Dooks <ben@simtec.co.uk>
+*/
+
+#ifndef __NET_AX88796_PLAT_H
+#define __NET_AX88796_PLAT_H
+
+#include <linux/types.h>
+
+struct sk_buff;
+struct net_device;
+struct platform_device;
+
+#define AXFLG_HAS_EEPROM		(1<<0)
+#define AXFLG_MAC_FROMDEV		(1<<1)	/* device already has MAC */
+#define AXFLG_HAS_93CX6			(1<<2)	/* use eeprom_93cx6 driver */
+#define AXFLG_MAC_FROMPLATFORM		(1<<3)	/* MAC given by platform data */
+
+struct ax_plat_data {
+	unsigned int	 flags;
+	unsigned char	 wordlength;	/* 1 or 2 */
+	unsigned char	 dcr_val;	/* default value for DCR */
+	unsigned char	 rcr_val;	/* default value for RCR */
+	unsigned char	 gpoc_val;	/* default value for GPOC */
+	u32		*reg_offsets;	/* register offsets */
+	u8		*mac_addr;	/* MAC addr (only used when
+					   AXFLG_MAC_FROMPLATFORM is used */
+
+	/* uses default ax88796 buffer if set to NULL */
+	void (*block_output)(struct net_device *dev, int count,
+			const unsigned char *buf, int star_page);
+	void (*block_input)(struct net_device *dev, int count,
+			struct sk_buff *skb, int ring_offset);
+	/* returns nonzero if a pending interrupt request might be caused by
+	 * the ax88796. Handles all interrupts if set to NULL
+	 */
+	int (*check_irq)(struct platform_device *pdev);
+};
+
+/* exported from ax88796.c for xsurf100.c  */
+extern void ax_NS8390_reinit(struct net_device *dev);
+
+#endif /* __NET_AX88796_PLAT_H */