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, 98 insertions, 0 deletions

diff --git a/tools/perf/util/target.h b/tools/perf/util/target.h
new file mode 100644
index 000000000..bc2bff9c6
--- /dev/null
+++ b/tools/perf/util/target.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PERF_TARGET_H
+#define _PERF_TARGET_H
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+struct target {
+	const char   *pid;
+	const char   *tid;
+	const char   *cpu_list;
+	const char   *bpf_str;
+	bool	     system_wide;
+	bool	     uses_mmap;
+	bool	     default_per_cpu;
+	bool	     per_thread;
+	bool	     use_bpf;
+	bool	     inherit;
+	int	     initial_delay;
+	const char   *attr_map;
+};
+
+enum target_errno {
+	TARGET_ERRNO__SUCCESS		= 0,
+
+	/*
+	 * Choose an arbitrary negative big number not to clash with standard
+	 * errno since SUS requires the errno has distinct positive values.
+	 * See 'Issue 6' in the link below.
+	 *
+	 * http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
+	 */
+	__TARGET_ERRNO__START		= -10000,
+
+	/* for target__validate() */
+	TARGET_ERRNO__PID_OVERRIDE_CPU	= __TARGET_ERRNO__START,
+	TARGET_ERRNO__PID_OVERRIDE_SYSTEM,
+	TARGET_ERRNO__SYSTEM_OVERRIDE_THREAD,
+	TARGET_ERRNO__BPF_OVERRIDE_CPU,
+	TARGET_ERRNO__BPF_OVERRIDE_PID,
+	TARGET_ERRNO__BPF_OVERRIDE_THREAD,
+
+	__TARGET_ERRNO__END,
+};
+
+enum target_errno target__validate(struct target *target);
+
+uid_t parse_uid(const char *str);
+
+int target__strerror(struct target *target, int errnum, char *buf, size_t buflen);
+
+static inline bool target__has_task(const struct target *target)
+{
+	return target->tid || target->pid;
+}
+
+static inline bool target__has_cpu(const struct target *target)
+{
+	return target->system_wide || target->cpu_list;
+}
+
+static inline bool target__none(const struct target *target)
+{
+	return !target__has_task(target) && !target__has_cpu(target);
+}
+
+static inline bool target__enable_on_exec(const struct target *target)
+{
+	/*
+	 * Normally enable_on_exec should be set if:
+	 *  1) The tracee process is forked (not attaching to existed task or cpu).
+	 *  2) And initial_delay is not configured.
+	 * Otherwise, we enable tracee events manually.
+	 */
+	return target__none(target) && !target->initial_delay;
+}
+
+static inline bool target__has_per_thread(const struct target *target)
+{
+	return target->system_wide && target->per_thread;
+}
+
+static inline bool target__uses_dummy_map(const struct target *target)
+{
+	bool use_dummy = false;
+
+	if (target->default_per_cpu)
+		use_dummy = target->per_thread ? true : false;
+	else if (target__has_task(target) ||
+	         (!target__has_cpu(target) && !target->uses_mmap))
+		use_dummy = true;
+	else if (target__has_per_thread(target))
+		use_dummy = true;
+
+	return use_dummy;
+}
+
+#endif /* _PERF_TARGET_H */