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, 40 insertions, 0 deletions

diff --git a/arch/mips/kvm/interrupt.c b/arch/mips/kvm/interrupt.c
new file mode 100644
index 000000000..895a6f178
--- /dev/null
+++ b/arch/mips/kvm/interrupt.c
@@ -0,0 +1,40 @@
+/*
+ * 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.
+ *
+ * KVM/MIPS: Interrupt delivery
+ *
+ * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
+ * Authors: Sanjay Lal <sanjayl@kymasys.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/vmalloc.h>
+#include <linux/fs.h>
+#include <linux/memblock.h>
+#include <asm/page.h>
+#include <asm/cacheflush.h>
+
+#include <linux/kvm_host.h>
+
+#include "interrupt.h"
+
+void kvm_mips_deliver_interrupts(struct kvm_vcpu *vcpu, u32 cause)
+{
+	unsigned long *pending = &vcpu->arch.pending_exceptions;
+	unsigned long *pending_clr = &vcpu->arch.pending_exceptions_clr;
+	unsigned int priority;
+
+	for_each_set_bit(priority, pending_clr, MIPS_EXC_MAX + 1)
+		kvm_mips_callbacks->irq_clear(vcpu, priority, cause);
+
+	for_each_set_bit(priority, pending, MIPS_EXC_MAX + 1)
+		kvm_mips_callbacks->irq_deliver(vcpu, priority, cause);
+}
+
+int kvm_mips_pending_timer(struct kvm_vcpu *vcpu)
+{
+	return test_bit(MIPS_EXC_INT_TIMER, &vcpu->arch.pending_exceptions);
+}