[PATCH v5 2/3] Input: applespi - fix NULL pointer dereference in tp_dim open
From: Shih-Yuan Lee <hidden>
Date: 2026-07-11 13:11:50
Also in:
linux-spi, lkml
Subsystem:
input (keyboard, mouse, joystick, touchscreen) drivers, the rest · Maintainers:
Dmitry Torokhov, Linus Torvalds
The tp_dim debugfs file is registered synchronously during driver probe in applespi_probe(). However, the applespi->touchpad_input_dev is initialized and registered asynchronously in the driver's worker thread. If a userspace process opens the debugfs file before the worker thread has completed initialization, applespi_tp_dim_open() will dereference the NULL applespi->touchpad_input_dev pointer, causing a kernel panic. Fix this by using smp_load_acquire() to safely load touchpad_input_dev and return -ENODEV if it is not yet initialized. Signed-off-by: Shih-Yuan Lee <redacted> --- drivers/input/keyboard/applespi.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/input/keyboard/applespi.c b/drivers/input/keyboard/applespi.c
index 3bdb9e7cfb8b..4d339445e9c7 100644
--- a/drivers/input/keyboard/applespi.c
+++ b/drivers/input/keyboard/applespi.c@@ -963,12 +963,18 @@ static void applespi_debug_update_dimensions(struct applespi_data *applespi, static int applespi_tp_dim_open(struct inode *inode, struct file *file) { struct applespi_data *applespi = inode->i_private; + struct input_dev *touchpad; file->private_data = applespi; + /* Pairs with smp_store_release in applespi_register_touchpad_device() */ + touchpad = smp_load_acquire(&applespi->touchpad_input_dev); + if (!touchpad) + return -ENODEV; + snprintf(applespi->tp_dim_val, sizeof(applespi->tp_dim_val), "0x%.4x %dx%d+%u+%u\n", - applespi->touchpad_input_dev->id.product, + touchpad->id.product, applespi->tp_dim_min_x, applespi->tp_dim_min_y, applespi->tp_dim_max_x - applespi->tp_dim_min_x, applespi->tp_dim_max_y - applespi->tp_dim_min_y);
--
2.39.5