tpm: fix double write race and tpm_release free issue
Moved the atomic_set of the data_pending variable until after the
tpm_read has completed processing. The existing code had a window of
time where a second write to the driver could clobber the tpm command
buffer.
Also fixed an issue where if close was called on the tpm device before a
read completed, the tpm command buffer would be returned to the OS,
which could contain sensitive information.
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 36e43e5..0a75638 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1171,7 +1171,7 @@
flush_work_sync(&chip->work);
file->private_data = NULL;
atomic_set(&chip->data_pending, 0);
- kfree(chip->data_buffer);
+ kzfree(chip->data_buffer);
clear_bit(0, &chip->is_open);
put_device(chip->dev);
return 0;
@@ -1223,7 +1223,6 @@
del_singleshot_timer_sync(&chip->user_read_timer);
flush_work_sync(&chip->work);
ret_size = atomic_read(&chip->data_pending);
- atomic_set(&chip->data_pending, 0);
if (ret_size > 0) { /* relay data */
ssize_t orig_ret_size = ret_size;
if (size < ret_size)
@@ -1238,6 +1237,8 @@
mutex_unlock(&chip->buffer_mutex);
}
+ atomic_set(&chip->data_pending, 0);
+
return ret_size;
}
EXPORT_SYMBOL_GPL(tpm_read);