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, 129 insertions, 0 deletions

diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
new file mode 100644
index 000000000..70232d8d0
--- /dev/null
+++ b/tools/perf/util/mutex.h
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_MUTEX_H
+#define __PERF_MUTEX_H
+
+#include <pthread.h>
+#include <stdbool.h>
+
+/*
+ * A function-like feature checking macro that is a wrapper around
+ * `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
+ * nonzero constant integer if the attribute is supported or 0 if not.
+ */
+#ifdef __has_attribute
+#define HAVE_ATTRIBUTE(x) __has_attribute(x)
+#else
+#define HAVE_ATTRIBUTE(x) 0
+#endif
+
+#if HAVE_ATTRIBUTE(guarded_by) && HAVE_ATTRIBUTE(pt_guarded_by) && \
+	HAVE_ATTRIBUTE(lockable) && HAVE_ATTRIBUTE(exclusive_lock_function) && \
+	HAVE_ATTRIBUTE(exclusive_trylock_function) && HAVE_ATTRIBUTE(exclusive_locks_required) && \
+	HAVE_ATTRIBUTE(no_thread_safety_analysis)
+
+/* Documents if a shared field or global variable needs to be protected by a mutex. */
+#define GUARDED_BY(x) __attribute__((guarded_by(x)))
+
+/*
+ * Documents if the memory location pointed to by a pointer should be guarded by
+ * a mutex when dereferencing the pointer.
+ */
+#define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
+
+/* Documents if a type is a lockable type. */
+#define LOCKABLE __attribute__((lockable))
+
+/* Documents a function that expects a lock not to be held prior to entry. */
+#define LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__)))
+
+/* Documents a function that returns a lock. */
+#define LOCK_RETURNED(x) __attribute__((lock_returned(x)))
+
+/* Documents functions that acquire a lock in the body of a function, and do not release it. */
+#define EXCLUSIVE_LOCK_FUNCTION(...)  __attribute__((exclusive_lock_function(__VA_ARGS__)))
+
+/*
+ * Documents functions that acquire a shared (reader) lock in the body of a
+ * function, and do not release it.
+ */
+#define SHARED_LOCK_FUNCTION(...)  __attribute__((shared_lock_function(__VA_ARGS__)))
+
+/*
+ * Documents functions that expect a lock to be held on entry to the function,
+ * and release it in the body of the function.
+ */
+#define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
+
+/* Documents functions that try to acquire a lock, and return success or failure. */
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
+	__attribute__((exclusive_trylock_function(__VA_ARGS__)))
+
+/* Documents a function that expects a mutex to be held prior to entry. */
+#define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
+
+/* Documents a function that expects a shared (reader) lock to be held prior to entry. */
+#define SHARED_LOCKS_REQUIRED(...) __attribute__((shared_locks_required(__VA_ARGS__)))
+
+/* Turns off thread safety checking within the body of a particular function. */
+#define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
+
+#else
+
+#define GUARDED_BY(x)
+#define PT_GUARDED_BY(x)
+#define LOCKABLE
+#define LOCKS_EXCLUDED(...)
+#define LOCK_RETURNED(x)
+#define EXCLUSIVE_LOCK_FUNCTION(...)
+#define SHARED_LOCK_FUNCTION(...)
+#define UNLOCK_FUNCTION(...)
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...)
+#define EXCLUSIVE_LOCKS_REQUIRED(...)
+#define SHARED_LOCKS_REQUIRED(...)
+#define NO_THREAD_SAFETY_ANALYSIS
+
+#endif
+
+/*
+ * A wrapper around the mutex implementation that allows perf to error check
+ * usage, etc.
+ */
+struct LOCKABLE mutex {
+	pthread_mutex_t lock;
+};
+
+/* A wrapper around the condition variable implementation. */
+struct cond {
+	pthread_cond_t cond;
+};
+
+/* Default initialize the mtx struct. */
+void mutex_init(struct mutex *mtx);
+/*
+ * Initialize the mtx struct and set the process-shared rather than default
+ * process-private attribute.
+ */
+void mutex_init_pshared(struct mutex *mtx);
+/* Initializes a mutex that may be recursively held on the same thread. */
+void mutex_init_recursive(struct mutex *mtx);
+void mutex_destroy(struct mutex *mtx);
+
+void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);
+void mutex_unlock(struct mutex *mtx) UNLOCK_FUNCTION(*mtx);
+/* Tries to acquire the lock and returns true on success. */
+bool mutex_trylock(struct mutex *mtx) EXCLUSIVE_TRYLOCK_FUNCTION(true, *mtx);
+
+/* Default initialize the cond struct. */
+void cond_init(struct cond *cnd);
+/*
+ * Initialize the cond struct and specify the process-shared rather than default
+ * process-private attribute.
+ */
+void cond_init_pshared(struct cond *cnd);
+void cond_destroy(struct cond *cnd);
+
+void cond_wait(struct cond *cnd, struct mutex *mtx) EXCLUSIVE_LOCKS_REQUIRED(mtx);
+void cond_signal(struct cond *cnd);
+void cond_broadcast(struct cond *cnd);
+
+#endif /* __PERF_MUTEX_H */