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, 125 insertions, 0 deletions

diff --git a/tools/perf/util/mutex.c b/tools/perf/util/mutex.c
new file mode 100644
index 000000000..7aa1f3f55
--- /dev/null
+++ b/tools/perf/util/mutex.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "mutex.h"
+
+#include "debug.h"
+#include <linux/string.h>
+#include <errno.h>
+
+static void check_err(const char *fn, int err)
+{
+	char sbuf[STRERR_BUFSIZE];
+
+	if (err == 0)
+		return;
+
+	pr_err("%s error: '%s'\n", fn, str_error_r(err, sbuf, sizeof(sbuf)));
+}
+
+#define CHECK_ERR(err) check_err(__func__, err)
+
+static void __mutex_init(struct mutex *mtx, bool pshared, bool recursive)
+{
+	pthread_mutexattr_t attr;
+
+	CHECK_ERR(pthread_mutexattr_init(&attr));
+
+#ifndef NDEBUG
+	/* In normal builds enable error checking, such as recursive usage. */
+	CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
+#endif
+	if (recursive)
+		CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE));
+	if (pshared)
+		CHECK_ERR(pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
+	CHECK_ERR(pthread_mutex_init(&mtx->lock, &attr));
+	CHECK_ERR(pthread_mutexattr_destroy(&attr));
+}
+
+void mutex_init(struct mutex *mtx)
+{
+	__mutex_init(mtx, /*pshared=*/false, /*recursive=*/false);
+}
+
+void mutex_init_pshared(struct mutex *mtx)
+{
+	__mutex_init(mtx, /*pshared=*/true, /*recursive=*/false);
+}
+
+void mutex_init_recursive(struct mutex *mtx)
+{
+	__mutex_init(mtx, /*pshared=*/false, /*recursive=*/true);
+}
+
+void mutex_destroy(struct mutex *mtx)
+{
+	CHECK_ERR(pthread_mutex_destroy(&mtx->lock));
+}
+
+void mutex_lock(struct mutex *mtx)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+	CHECK_ERR(pthread_mutex_lock(&mtx->lock));
+}
+
+void mutex_unlock(struct mutex *mtx)
+	NO_THREAD_SAFETY_ANALYSIS
+{
+	CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
+}
+
+bool mutex_trylock(struct mutex *mtx)
+{
+	int ret = pthread_mutex_trylock(&mtx->lock);
+
+	if (ret == 0)
+		return true; /* Lock acquired. */
+
+	if (ret == EBUSY)
+		return false; /* Lock busy. */
+
+	/* Print error. */
+	CHECK_ERR(ret);
+	return false;
+}
+
+static void __cond_init(struct cond *cnd, bool pshared)
+{
+	pthread_condattr_t attr;
+
+	CHECK_ERR(pthread_condattr_init(&attr));
+	if (pshared)
+		CHECK_ERR(pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
+
+	CHECK_ERR(pthread_cond_init(&cnd->cond, &attr));
+	CHECK_ERR(pthread_condattr_destroy(&attr));
+}
+
+void cond_init(struct cond *cnd)
+{
+	__cond_init(cnd, /*pshared=*/false);
+}
+
+void cond_init_pshared(struct cond *cnd)
+{
+	__cond_init(cnd, /*pshared=*/true);
+}
+
+void cond_destroy(struct cond *cnd)
+{
+	CHECK_ERR(pthread_cond_destroy(&cnd->cond));
+}
+
+void cond_wait(struct cond *cnd, struct mutex *mtx)
+{
+	CHECK_ERR(pthread_cond_wait(&cnd->cond, &mtx->lock));
+}
+
+void cond_signal(struct cond *cnd)
+{
+	CHECK_ERR(pthread_cond_signal(&cnd->cond));
+}
+
+void cond_broadcast(struct cond *cnd)
+{
+	CHECK_ERR(pthread_cond_broadcast(&cnd->cond));
+}