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, 71 insertions, 0 deletions

diff --git a/tools/perf/util/rwsem.c b/tools/perf/util/rwsem.c
new file mode 100644
index 000000000..9d2683239
--- /dev/null
+++ b/tools/perf/util/rwsem.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "util.h"
+#include "rwsem.h"
+
+#if RWS_ERRORCHECK
+#include "mutex.h"
+#endif
+
+int init_rwsem(struct rw_semaphore *sem)
+{
+#if RWS_ERRORCHECK
+	mutex_init(&sem->mtx);
+	return 0;
+#else
+	return pthread_rwlock_init(&sem->lock, NULL);
+#endif
+}
+
+int exit_rwsem(struct rw_semaphore *sem)
+{
+#if RWS_ERRORCHECK
+	mutex_destroy(&sem->mtx);
+	return 0;
+#else
+	return pthread_rwlock_destroy(&sem->lock);
+#endif
+}
+
+int down_read(struct rw_semaphore *sem)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+#if RWS_ERRORCHECK
+	mutex_lock(&sem->mtx);
+	return 0;
+#else
+	return perf_singlethreaded ? 0 : pthread_rwlock_rdlock(&sem->lock);
+#endif
+}
+
+int up_read(struct rw_semaphore *sem)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+#if RWS_ERRORCHECK
+	mutex_unlock(&sem->mtx);
+	return 0;
+#else
+	return perf_singlethreaded ? 0 : pthread_rwlock_unlock(&sem->lock);
+#endif
+}
+
+int down_write(struct rw_semaphore *sem)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+#if RWS_ERRORCHECK
+	mutex_lock(&sem->mtx);
+	return 0;
+#else
+	return perf_singlethreaded ? 0 : pthread_rwlock_wrlock(&sem->lock);
+#endif
+}
+
+int up_write(struct rw_semaphore *sem)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+#if RWS_ERRORCHECK
+	mutex_unlock(&sem->mtx);
+	return 0;
+#else
+	return perf_singlethreaded ? 0 : pthread_rwlock_unlock(&sem->lock);
+#endif
+}