[PATCH] Input: synaptics-rmi4 - remove the F34 sysfs group when probe fails

[Wei Jie Law <98lawweijie@gmail.com>]

rmi_driver_probe() creates the F34 firmware attribute group directly on
the rmi_device's kobject:

	retval = rmi_f34_create_sysfs(rmi_dev);
	if (retval)
		goto err;

but rmi_f34_remove_sysfs() is only ever called from
rmi_driver_remove(), which does not run when probe fails.  Every error
path taken after that point -- input_register_device(), rmi_irq_init(),
rmi_enable_sensor() -- therefore leaves the group in place on a device
that never finished binding.

The driver core clears the device's driver data when probe fails, so
what is left behind is a set of world-readable attributes whose show()
handlers dereference that now-NULL pointer:

	static ssize_t rmi_driver_bootloader_id_show(struct device *dev, ...)
	{
		struct rmi_driver_data *data = dev_get_drvdata(dev);
		struct rmi_function *fn;

		fn = data->f34_container;

bootloader_id, configuration_id and update_fw_status are all mode 0444,
so any local user can dereference it.  Reaching the failure does not
need privileges either: a device that simply stops answering a register
read makes rmi_enable_sensor() fail, which is past the group creation.

An emulated RMI4 touchpad over /dev/uhid that leaves the second read of
the F01 interrupt-status register unanswered, on v6.12.105 with
CONFIG_KASAN=y:

  rmi4_physical rmi4-00: Failed to read irqs, code=-11
  rmi4_physical rmi4-00: probe with driver rmi4_physical failed with error -11

and then, from an ordinary user:

  $ cat /sys/bus/rmi4/devices/rmi4-00/bootloader_id

  Oops: general protection fault, probably for non-canonical address
        0xdffffc0000000004: 0000 [#1] PREEMPT SMP KASAN NOPTI
  KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
  CPU: 0 UID: 1000 PID: 1851 Comm: cat Tainted: G            E
  RIP: 0010:rmi_driver_bootloader_id_show+0x4d/0x1b0 [rmi_core]
   dev_attr_show+0x46/0xc0
   sysfs_kf_seq_show+0x1f1/0x3c0
   seq_read_iter+0x2f8/0x1150
   vfs_read+0x699/0xa00

one oops per attribute.

Add an err_remove_sysfs label that drops the group, and route the error
paths below rmi_f34_create_sysfs() through it.  rmi_f34_create_sysfs()
failing on its own account goes to err_destroy_functions instead, which
also repairs a second leak on that path: it used to "goto err" and skip
rmi_free_function_list() entirely, leaving the function devices
registered on the RMI bus with a parent whose driver data is gone.  The
resulting order matches rmi_driver_remove().

After this change the same device leaves no attributes behind, the reads
fail with -ENOENT, and no oops is reported; a well-behaved device still
probes and keeps its F34 group.

Fixes: 29fd0ec2bdbe ("Input: synaptics-rmi4 - add support for F34 device reflash")
Cc: stable@vger.kernel.org
Signed-off-by: Wei Jie Law <98lawweijie@gmail.com>
---
 drivers/input/rmi4/rmi_driver.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/input/rmi4/rmi_driver.c b/drivers/input/rmi4/rmi_driver.c
index 5d49a9021c7d..144b203e636a 100644
--- a/drivers/input/rmi4/rmi_driver.c
+++ b/drivers/input/rmi4/rmi_driver.c
@@ -1255,7 +1255,7 @@ static int rmi_driver_probe(struct device *dev)
 
 	retval = rmi_f34_create_sysfs(rmi_dev);
 	if (retval)
-		goto err;
+		goto err_destroy_functions;
 
 	if (data->input) {
 		rmi_driver_set_input_name(rmi_dev, data->input);
@@ -1264,14 +1264,14 @@ static int rmi_driver_probe(struct device *dev)
 			if (retval) {
 				dev_err(dev, "%s: Failed to register input device.\n",
 					__func__);
-				goto err_destroy_functions;
+				goto err_remove_sysfs;
 			}
 		}
 	}
 
 	retval = rmi_irq_init(rmi_dev);
 	if (retval < 0)
-		goto err_destroy_functions;
+		goto err_remove_sysfs;
 
 	if (data->f01_container->dev.driver) {
 		/* Driver already bound, so enable ATTN now. */
@@ -1284,6 +1284,8 @@ static int rmi_driver_probe(struct device *dev)
 
 err_disable_irq:
 	rmi_disable_irq(rmi_dev, false);
+err_remove_sysfs:
+	rmi_f34_remove_sysfs(rmi_dev);
 err_destroy_functions:
 	rmi_free_function_list(rmi_dev);
 err:
-- 
2.43.0