The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x f4d1960764d8a70318b02f15203a1be2b2554ca1 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024040119-ranked-doormat-088b@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..
Possible dependencies:
f4d1960764d8 ("USB: core: Fix deadlock in port "disable" sysfs attribute") f061f43d7418 ("usb: hub: port: add sysfs entry to switch port power") 8c67d06f3fd9 ("usb: Link the ports to the connectors they are attached to") b8f1ba99cea5 ("usb: hub: make wait_for_connected() take an int instead of a pointer to int") f59f93cd1d72 ("usb: hub: avoid warm port reset during USB3 disconnect") 7142452387c7 ("USB: Verify the port status when timeout happens during port suspend") 975f94c7d6c3 ("usb: core: hub: fix race condition about TRSMRCY of resume") 355c74e55e99 ("usb: export firmware port location in sysfs")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f4d1960764d8a70318b02f15203a1be2b2554ca1 Mon Sep 17 00:00:00 2001 From: Alan Stern stern@rowland.harvard.edu Date: Fri, 15 Mar 2024 13:06:33 -0400 Subject: [PATCH] USB: core: Fix deadlock in port "disable" sysfs attribute
The show and store callback routines for the "disable" sysfs attribute file in port.c acquire the device lock for the port's parent hub device. This can cause problems if another process has locked the hub to remove it or change its configuration:
Removing the hub or changing its configuration requires the hub interface to be removed, which requires the port device to be removed, and device_del() waits until all outstanding sysfs attribute callbacks for the ports have returned. The lock can't be released until then.
But the disable_show() or disable_store() routine can't return until after it has acquired the lock.
The resulting deadlock can be avoided by calling sysfs_break_active_protection(). This will cause the sysfs core not to wait for the attribute's callback routine to return, allowing the removal to proceed. The disadvantage is that after making this call, there is no guarantee that the hub structure won't be deallocated at any moment. To prevent this, we have to acquire a reference to it first by calling hub_get().
Signed-off-by: Alan Stern stern@rowland.harvard.edu Cc: stable stable@kernel.org Link: https://lore.kernel.org/r/f7a8c135-a495-4ce6-bd49-405a45e7ea9a@rowland.harva... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c index 5b5e613a11e5..686c01af03e6 100644 --- a/drivers/usb/core/port.c +++ b/drivers/usb/core/port.c @@ -56,11 +56,22 @@ static ssize_t disable_show(struct device *dev, u16 portstatus, unused; bool disabled; int rc; + struct kernfs_node *kn;
+ hub_get(hub); rc = usb_autopm_get_interface(intf); if (rc < 0) - return rc; + goto out_hub_get;
+ /* + * Prevent deadlock if another process is concurrently + * trying to unregister hdev. + */ + kn = sysfs_break_active_protection(&dev->kobj, &attr->attr); + if (!kn) { + rc = -ENODEV; + goto out_autopm; + } usb_lock_device(hdev); if (hub->disconnected) { rc = -ENODEV; @@ -70,9 +81,13 @@ static ssize_t disable_show(struct device *dev, usb_hub_port_status(hub, port1, &portstatus, &unused); disabled = !usb_port_is_power_on(hub, portstatus);
-out_hdev_lock: + out_hdev_lock: usb_unlock_device(hdev); + sysfs_unbreak_active_protection(kn); + out_autopm: usb_autopm_put_interface(intf); + out_hub_get: + hub_put(hub);
if (rc) return rc; @@ -90,15 +105,26 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr, int port1 = port_dev->portnum; bool disabled; int rc; + struct kernfs_node *kn;
rc = kstrtobool(buf, &disabled); if (rc) return rc;
+ hub_get(hub); rc = usb_autopm_get_interface(intf); if (rc < 0) - return rc; + goto out_hub_get;
+ /* + * Prevent deadlock if another process is concurrently + * trying to unregister hdev. + */ + kn = sysfs_break_active_protection(&dev->kobj, &attr->attr); + if (!kn) { + rc = -ENODEV; + goto out_autopm; + } usb_lock_device(hdev); if (hub->disconnected) { rc = -ENODEV; @@ -119,9 +145,13 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr, if (!rc) rc = count;
-out_hdev_lock: + out_hdev_lock: usb_unlock_device(hdev); + sysfs_unbreak_active_protection(kn); + out_autopm: usb_autopm_put_interface(intf); + out_hub_get: + hub_put(hub);
return rc; }