[PATCH 6.1.y] usb: typec: altmodes/displayport: create sysfs nodes as driver's default device attribute group

[PATCH 6.1.y] usb: typec: altmodes/displayport: create sysfs nodes as driver's default device attribute group

[jianqi.ren.cn]

From: RD Babiera <rdbabiera@google.com>

commit 165376f6b23e9a779850e750fb2eb06622e5a531 upstream.

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>
Link: https://lore.kernel.org/r/20240229001101.3889432-2-rdbabiera@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[Minor conflict resolved due to code context change.]
Signed-off-by: Jianqi Ren <jianqi.ren.cn@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
Verified the build test
---
 drivers/usb/typec/altmodes/displayport.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index f564d0d471bb..f80124102328 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -543,15 +543,20 @@ static ssize_t pin_assignment_show(struct device *dev,
 }
 static DEVICE_ATTR_RW(pin_assignment);
 
-static struct attribute *dp_altmode_attrs[] = {
+static struct attribute *displayport_attrs[] = {
 	&dev_attr_configuration.attr,
 	&dev_attr_pin_assignment.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)
@@ -559,7 +564,6 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	const struct typec_altmode *port = typec_altmode_get_partner(alt);
 	struct fwnode_handle *fwnode;
 	struct dp_altmode *dp;
-	int ret;
 
 	/* FIXME: Port can only be DFP_U. */
 
@@ -570,10 +574,6 @@ 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;
@@ -604,7 +604,6 @@ 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);
 
 	if (dp->connector_fwnode) {
@@ -629,6 +628,7 @@ 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);
-- 
2.34.1

Re: [PATCH 6.1.y] usb: typec: altmodes/displayport: create sysfs nodes as driver's default device attribute group

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 165376f6b23e9a779850e750fb2eb06622e5a531

WARNING: Author mismatch between patch and upstream commit:
Backport author: <jianqi.ren.cn@windriver.com>
Commit author: RD Babiera<rdbabiera@google.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: 4a22aeac24d0)

Note: The patch differs from the upstream commit:
---
1:  165376f6b23e9 ! 1:  e6db96b46a3d1 usb: typec: altmodes/displayport: create sysfs nodes as driver's default device attribute group
    @@ Metadata
      ## Commit message ##
         usb: typec: altmodes/displayport: create sysfs nodes as driver's default device attribute group
     
    +    commit 165376f6b23e9a779850e750fb2eb06622e5a531 upstream.
    +
         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
    @@ Commit message
         Signed-off-by: RD Babiera <rdbabiera@google.com>
         Link: https://lore.kernel.org/r/20240229001101.3889432-2-rdbabiera@google.com
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    +    [Minor conflict resolved due to code context change.]
    +    Signed-off-by: Jianqi Ren <jianqi.ren.cn@windriver.com>
    +    Signed-off-by: He Zhe <zhe.he@windriver.com>
     
      ## drivers/usb/typec/altmodes/displayport.c ##
    -@@ drivers/usb/typec/altmodes/displayport.c: static ssize_t hpd_show(struct device *dev, struct device_attribute *attr, char
    +@@ drivers/usb/typec/altmodes/displayport.c: static ssize_t pin_assignment_show(struct device *dev,
      }
    - static DEVICE_ATTR_RO(hpd);
    + static DEVICE_ATTR_RW(pin_assignment);
      
     -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
      };
      
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |