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, 99 insertions, 0 deletions

diff --git a/include/trace/events/task.h b/include/trace/events/task.h
new file mode 100644
index 000000000..b9a129eb5
--- /dev/null
+++ b/include/trace/events/task.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM task
+
+#if !defined(_TRACE_TASK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TASK_H
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(task_newtask,
+
+	TP_PROTO(struct task_struct *task, u64 clone_flags),
+
+	TP_ARGS(task, clone_flags),
+
+	TP_STRUCT__entry(
+		__field(	pid_t,	pid)
+		__array(	char,	comm, TASK_COMM_LEN)
+		__field(	u64,    clone_flags)
+		__field(	short,	oom_score_adj)
+	),
+
+	TP_fast_assign(
+		__entry->pid = task->pid;
+		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+		__entry->clone_flags = clone_flags;
+		__entry->oom_score_adj = task->signal->oom_score_adj;
+	),
+
+	TP_printk("pid=%d comm=%s clone_flags=%llx oom_score_adj=%hd",
+		__entry->pid, __entry->comm,
+		__entry->clone_flags, __entry->oom_score_adj)
+);
+
+TRACE_EVENT(task_rename,
+
+	TP_PROTO(struct task_struct *task, const char *comm),
+
+	TP_ARGS(task, comm),
+
+	TP_STRUCT__entry(
+		__field(	pid_t,	pid)
+		__array(	char, oldcomm,  TASK_COMM_LEN)
+		__array(	char, newcomm,  TASK_COMM_LEN)
+		__field(	short,	oom_score_adj)
+	),
+
+	TP_fast_assign(
+		__entry->pid = task->pid;
+		memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
+		strscpy(entry->newcomm, comm, TASK_COMM_LEN);
+		__entry->oom_score_adj = task->signal->oom_score_adj;
+	),
+
+	TP_printk("pid=%d oldcomm=%s newcomm=%s oom_score_adj=%hd",
+		__entry->pid, __entry->oldcomm,
+		__entry->newcomm, __entry->oom_score_adj)
+);
+
+/**
+ * task_prctl_unknown - called on unknown prctl() option
+ * @option:	option passed
+ * @arg2:	arg2 passed
+ * @arg3:	arg3 passed
+ * @arg4:	arg4 passed
+ * @arg5:	arg5 passed
+ *
+ * Called on an unknown prctl() option.
+ */
+TRACE_EVENT(task_prctl_unknown,
+
+	TP_PROTO(int option, unsigned long arg2, unsigned long arg3,
+		 unsigned long arg4, unsigned long arg5),
+
+	TP_ARGS(option, arg2, arg3, arg4, arg5),
+
+	TP_STRUCT__entry(
+		__field(	int,		option)
+		__field(	unsigned long,	arg2)
+		__field(	unsigned long,	arg3)
+		__field(	unsigned long,	arg4)
+		__field(	unsigned long,	arg5)
+	),
+
+	TP_fast_assign(
+		__entry->option = option;
+		__entry->arg2 = arg2;
+		__entry->arg3 = arg3;
+		__entry->arg4 = arg4;
+		__entry->arg5 = arg5;
+	),
+
+	TP_printk("option=%d arg2=%ld arg3=%ld arg4=%ld arg5=%ld",
+		  __entry->option, __entry->arg2, __entry->arg3, __entry->arg4, __entry->arg5)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>