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Message-ID: <20240110095814.7626-1-quic_ugoswami@quicinc.com>
Date: Wed, 10 Jan 2024 15:28:14 +0530
From: Udipto Goswami <quic_ugoswami@...cinc.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Alan Stern
<stern@...land.harvard.edu>
CC: Krishna Kurapati <quic_kriskura@...cinc.com>,
Sergei Shtylyov
<sergei.shtylyov@...il.com>,
<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<stable@...r.kernel.org>, Udipto Goswami
<quic_ugoswami@...cinc.com>
Subject: [PATCH v5] usb: core: Prevent null pointer dereference in update_port_device_state
Currently, the function update_port_device_state gets the usb_hub from
udev->parent by calling usb_hub_to_struct_hub.
However, in case the actconfig or the maxchild is 0, the usb_hub would
be NULL and upon further accessing to get port_dev would result in null
pointer dereference.
Fix this by introducing an if check after the usb_hub is populated.
Fixes: 83cb2604f641 ("usb: core: add sysfs entry for usb device state")
Cc: stable@...r.kernel.org
Signed-off-by: Udipto Goswami <quic_ugoswami@...cinc.com>
---
v5: Addressed nit picks in commit and the comment.
v4: Fixed minor mistakes in the comment.
v3: Re-wrote the comment for better context.
v2: Introduced comment for the if check & CC'ed stable.
drivers/usb/core/hub.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index ffd7c99e24a3..48409d51ea43 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2053,9 +2053,19 @@ static void update_port_device_state(struct usb_device *udev)
if (udev->parent) {
hub = usb_hub_to_struct_hub(udev->parent);
- port_dev = hub->ports[udev->portnum - 1];
- WRITE_ONCE(port_dev->state, udev->state);
- sysfs_notify_dirent(port_dev->state_kn);
+
+ /*
+ * The Link Layer Validation System Driver (lvstest)
+ * has a test step to unbind the hub before running the
+ * rest of the procedure. This triggers hub_disconnect
+ * which will set the hub's maxchild to 0, further
+ * resulting in usb_hub_to_struct_hub returning NULL.
+ */
+ if (hub) {
+ port_dev = hub->ports[udev->portnum - 1];
+ WRITE_ONCE(port_dev->state, udev->state);
+ sysfs_notify_dirent(port_dev->state_kn);
+ }
}
}
--
2.17.1
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