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, 52 insertions, 0 deletions

diff --git a/sound/firewire/cmp.h b/sound/firewire/cmp.h
new file mode 100644
index 000000000..66fc08b74
--- /dev/null
+++ b/sound/firewire/cmp.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef SOUND_FIREWIRE_CMP_H_INCLUDED
+#define SOUND_FIREWIRE_CMP_H_INCLUDED
+
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include "iso-resources.h"
+
+struct fw_unit;
+
+enum cmp_direction {
+	CMP_INPUT = 0,
+	CMP_OUTPUT,
+};
+
+/**
+ * struct cmp_connection - manages an isochronous connection to a device
+ * @speed: the connection's actual speed
+ *
+ * This structure manages (using CMP) an isochronous stream between the local
+ * computer and a device's input plug (iPCR) and output plug (oPCR).
+ *
+ * There is no corresponding oPCR created on the local computer, so it is not
+ * possible to overlay connections on top of this one.
+ */
+struct cmp_connection {
+	int speed;
+	/* private: */
+	bool connected;
+	struct mutex mutex;
+	struct fw_iso_resources resources;
+	__be32 last_pcr_value;
+	unsigned int pcr_index;
+	unsigned int max_speed;
+	enum cmp_direction direction;
+};
+
+int cmp_connection_init(struct cmp_connection *connection,
+			struct fw_unit *unit,
+			enum cmp_direction direction,
+			unsigned int pcr_index);
+int cmp_connection_check_used(struct cmp_connection *connection, bool *used);
+void cmp_connection_destroy(struct cmp_connection *connection);
+
+int cmp_connection_reserve(struct cmp_connection *connection,
+			   unsigned int max_payload);
+void cmp_connection_release(struct cmp_connection *connection);
+
+int cmp_connection_establish(struct cmp_connection *connection);
+void cmp_connection_break(struct cmp_connection *connection);
+
+#endif