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, 100 insertions, 0 deletions

diff --git a/arch/m68k/sun3/sun3ints.c b/arch/m68k/sun3/sun3ints.c
new file mode 100644
index 000000000..32eaf55f8
--- /dev/null
+++ b/arch/m68k/sun3/sun3ints.c
@@ -0,0 +1,100 @@
+ /*
+ * linux/arch/m68k/sun3/sun3ints.c -- Sun-3(x) Linux interrupt handling code
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/kernel_stat.h>
+#include <linux/interrupt.h>
+#include <asm/intersil.h>
+#include <asm/oplib.h>
+#include <asm/sun3ints.h>
+#include <asm/irq_regs.h>
+#include <linux/seq_file.h>
+
+#include "sun3.h"
+
+void sun3_disable_interrupts(void)
+{
+	sun3_disable_irq(0);
+}
+
+void sun3_enable_interrupts(void)
+{
+	sun3_enable_irq(0);
+}
+
+static unsigned char led_pattern[8] = {
+	(u8)~(0x80), (u8)~(0x01),
+	(u8)~(0x40), (u8)~(0x02),
+	(u8)~(0x20), (u8)~(0x04),
+	(u8)~(0x10), (u8)~(0x08)
+};
+
+volatile unsigned char* sun3_intreg;
+
+void sun3_enable_irq(unsigned int irq)
+{
+	*sun3_intreg |=  (1 << irq);
+}
+
+void sun3_disable_irq(unsigned int irq)
+{
+	*sun3_intreg &= ~(1 << irq);
+}
+
+static irqreturn_t sun3_int7(int irq, void *dev_id)
+{
+	unsigned int cnt;
+
+	cnt = kstat_irqs_cpu(irq, 0);
+	if (!(cnt % 2000))
+		sun3_leds(led_pattern[cnt % 16000 / 2000]);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sun3_int5(int irq, void *dev_id)
+{
+	unsigned long flags;
+	unsigned int cnt;
+
+	local_irq_save(flags);
+#ifdef CONFIG_SUN3
+	intersil_clear();
+#endif
+	sun3_disable_irq(5);
+	sun3_enable_irq(5);
+#ifdef CONFIG_SUN3
+	intersil_clear();
+#endif
+	legacy_timer_tick(1);
+	cnt = kstat_irqs_cpu(irq, 0);
+	if (!(cnt % 20))
+		sun3_leds(led_pattern[cnt % 160 / 20]);
+	local_irq_restore(flags);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sun3_vec255(int irq, void *dev_id)
+{
+	return IRQ_HANDLED;
+}
+
+void __init sun3_init_IRQ(void)
+{
+	*sun3_intreg = 1;
+
+	m68k_setup_user_interrupt(VEC_USER, 128);
+
+	if (request_irq(IRQ_AUTO_5, sun3_int5, 0, "clock", NULL))
+		pr_err("Couldn't register %s interrupt\n", "int5");
+	if (request_irq(IRQ_AUTO_7, sun3_int7, 0, "nmi", NULL))
+		pr_err("Couldn't register %s interrupt\n", "int7");
+	if (request_irq(IRQ_USER+127, sun3_vec255, 0, "vec255", NULL))
+		pr_err("Couldn't register %s interrupt\n", "vec255");
+}