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, 33 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h
new file mode 100644
index 000000000..f3742bcc7
--- /dev/null
+++ b/drivers/char/tpm/tpm-dev.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TPM_DEV_H
+#define _TPM_DEV_H
+
+#include <linux/poll.h>
+#include "tpm.h"
+
+struct file_priv {
+	struct tpm_chip *chip;
+	struct tpm_space *space;
+
+	struct mutex buffer_mutex;
+	struct timer_list user_read_timer;      /* user needs to claim result */
+	struct work_struct timeout_work;
+	struct work_struct async_work;
+	wait_queue_head_t async_wait;
+	ssize_t response_length;
+	bool response_read;
+	bool command_enqueued;
+
+	u8 data_buffer[TPM_BUFSIZE];
+};
+
+void tpm_common_open(struct file *file, struct tpm_chip *chip,
+		     struct file_priv *priv, struct tpm_space *space);
+ssize_t tpm_common_read(struct file *file, char __user *buf,
+			size_t size, loff_t *off);
+ssize_t tpm_common_write(struct file *file, const char __user *buf,
+			 size_t size, loff_t *off);
+__poll_t tpm_common_poll(struct file *file, poll_table *wait);
+
+void tpm_common_release(struct file *file, struct file_priv *priv);
+#endif