Input: edt-ft5x06 - fix use-after-free in debugfs teardown

The commit 68743c5 ("Input: edt-ft5x06 - use per-client debugfs
directory") removed the manual debugfs teardown, relying on the I2C core
to handle it. However, this creates a window where debugfs files are
still accessible after edt_ft5x06_ts_teardown_debugfs() frees
tsdata->raw_buffer.

To prevent a use-after-free, protect the freeing of raw_buffer with the
device mutex and set raw_buffer to NULL. The debugfs read function
already checks if raw_buffer is NULL under the same mutex, so this
safely avoids the use-after-free.

Fixes: 68743c5 ("Input: edt-ft5x06 - use per-client debugfs directory")
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dmitry Torokhov <[email protected]>

Author: dtor

drivers/input/touchscreen/edt-ft5x06.c

@@ -804,7 +804,10 @@ static void edt_ft5x06_ts_prepare_debugfs(struct edt_ft5x06_ts_data *tsdata)
 
 static void edt_ft5x06_ts_teardown_debugfs(struct edt_ft5x06_ts_data *tsdata)
 {
+	guard(mutex)(&tsdata->mutex);
+
 	kfree(tsdata->raw_buffer);
+	tsdata->raw_buffer = NULL;
 }
 
 #else