On Thu, Feb 29, 2024 at 12:11:02AM +0000, RD Babiera wrote:

The DisplayPort driver's sysfs nodes may be present to the userspace before typec_altmode_set_drvdata() completes in dp_altmode_probe. This means that a sysfs read can trigger a NULL pointer error by deferencing dp->hpd in hpd_show or dp->lock in pin_assignment_show, as dev_get_drvdata() returns NULL in those cases.

Remove manual sysfs node creation in favor of adding attribute group as default for devices bound to the driver. The ATTRIBUTE_GROUPS() macro is not used here otherwise the path to the sysfs nodes is no longer compliant with the ABI.

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode") Cc: stable@vger.kernel.org Signed-off-by: RD Babiera rdbabiera@google.com

Reviewed-by: Heikki Krogerus heikki.krogerus@linux.intel.com

---

Changes from v1:

• Moved sysfs node creation instead of NULL checking dev_get_drvdata().

Changes from v2:

• Removed manual sysfs node creation, now added as default device group in

driver.

drivers/usb/typec/altmodes/displayport.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/us<F16>b/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c index 5a80776c7255..94e1b43a862d 100644 --- a/drivers/usb/typec/altmodes/displayport.c +++ b/drivers/usb/typec/altmodes/displayport.c @@ -702,16 +702,21 @@ static ssize_t hpd_show(struct device *dev, struct device_attribute *attr, char } static DEVICE_ATTR_RO(hpd); -static struct attribute *dp_altmode_attrs[] = { +static struct attribute *displayport_attrs[] = { &dev_attr_configuration.attr, &dev_attr_pin_assignment.attr, &dev_attr_hpd.attr, NULL }; -static const struct attribute_group dp_altmode_group = { +static const struct attribute_group displayport_group = { .name = "displayport",

• .attrs = dp_altmode_attrs,

• .attrs = displayport_attrs,

+};

+static const struct attribute_group *displayport_groups[] = {

• &displayport_group,
• NULL,

}; int dp_altmode_probe(struct typec_altmode *alt) @@ -720,7 +725,6 @@ int dp_altmode_probe(struct typec_altmode *alt) struct typec_altmode *plug = typec_altmode_get_plug(alt, TYPEC_PLUG_SOP_P); struct fwnode_handle *fwnode; struct dp_altmode *dp;

• int ret;

/* FIXME: Port can only be DFP_U. */ @@ -731,10 +735,6 @@ int dp_altmode_probe(struct typec_altmode *alt) DP_CAP_PIN_ASSIGN_DFP_D(alt->vdo))) return -ENODEV;

• ret = sysfs_create_group(&alt->dev.kobj, &dp_altmode_group);
• if (ret)

• return ret;
  

• dp = devm_kzalloc(&alt->dev, sizeof(*dp), GFP_KERNEL); if (!dp) return -ENOMEM;

@@ -777,7 +777,6 @@ void dp_altmode_remove(struct typec_altmode *alt) { struct dp_altmode *dp = typec_altmode_get_drvdata(alt);

• sysfs_remove_group(&alt->dev.kobj, &dp_altmode_group); cancel_work_sync(&dp->work); typec_altmode_put_plug(dp->plug_prime);

@@ -803,6 +802,7 @@ static struct typec_altmode_driver dp_altmode_driver = { .driver = { .name = "typec_displayport", .owner = THIS_MODULE,

• .dev_groups = displayport_groups,
  

  },

}; module_typec_altmode_driver(dp_altmode_driver);

base-commit: a560a5672826fc1e057068bda93b3d4c98d037a2

2.44.0.rc1.240.g4c46232300-goog