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, 63 insertions, 0 deletions

diff --git a/arch/mips/kvm/stats.c b/arch/mips/kvm/stats.c
new file mode 100644
index 000000000..3e6682018
--- /dev/null
+++ b/arch/mips/kvm/stats.c
@@ -0,0 +1,63 @@
+/*
+ * 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: COP0 access histogram
+ *
+ * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
+ * Authors: Sanjay Lal <sanjayl@kymasys.com>
+ */
+
+#include <linux/kvm_host.h>
+
+char *kvm_cop0_str[N_MIPS_COPROC_REGS] = {
+	"Index",
+	"Random",
+	"EntryLo0",
+	"EntryLo1",
+	"Context",
+	"PG Mask",
+	"Wired",
+	"HWREna",
+	"BadVAddr",
+	"Count",
+	"EntryHI",
+	"Compare",
+	"Status",
+	"Cause",
+	"EXC PC",
+	"PRID",
+	"Config",
+	"LLAddr",
+	"Watch Lo",
+	"Watch Hi",
+	"X Context",
+	"Reserved",
+	"Impl Dep",
+	"Debug",
+	"DEPC",
+	"PerfCnt",
+	"ErrCtl",
+	"CacheErr",
+	"TagLo",
+	"TagHi",
+	"ErrorEPC",
+	"DESAVE"
+};
+
+void kvm_mips_dump_stats(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
+	int i, j;
+
+	kvm_info("\nKVM VCPU[%d] COP0 Access Profile:\n", vcpu->vcpu_id);
+	for (i = 0; i < N_MIPS_COPROC_REGS; i++) {
+		for (j = 0; j < N_MIPS_COPROC_SEL; j++) {
+			if (vcpu->arch.cop0.stat[i][j])
+				kvm_info("%s[%d]: %lu\n", kvm_cop0_str[i], j,
+					 vcpu->arch.cop0.stat[i][j]);
+		}
+	}
+#endif
+}