linux-kernel - [PATCH v3] USB: usbip: fix null-ptr-deref in status_show

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Message-Id: <20250122125857.25157-1-qasdev00@gmail.com>
Date: Wed, 22 Jan 2025 12:58:57 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: valentina.manea.m@...il.com,
	shuah@...nel.org,
	i@...ithal.me,
	gregkh@...uxfoundation.org,
	sergei.shtylyov@...il.com
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
Subject: [PATCH v3] USB: usbip: fix null-ptr-deref in status_show_vhci()

If usb_add_hcd() fails in vhci_hcd_probe() (i.e., a probe failure),
the error path calls usb_remove_hcd() and also sets 
pdev->dev.driver_data to NULL.

Consequently, any subsequent call to platform_get_drvdata(pdev) 
(which returns pdev->dev.driver_data) may yield NULL, causing a 
crash if that pointer is dereferenced.

Fix this by adding a sanity check to ensure "hcd" is non-NULL
before proceeding with further operations.

Reported-by: syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=83976e47ec1ef91e66f1
Tested-by: syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
Fixes: 03cd00d538a6 ("usbip: vhci-hcd: Set the vhci structure up to work")
Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
---
v3:
- Added this section to comply with patch format requirements
- Removed the extra newline after `hcd = platform_get_drvdata(pdev);`

 drivers/usb/usbip/vhci_sysfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index d5865460e82d..d4a1aa6d06b2 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -76,6 +76,9 @@ static ssize_t status_show_vhci(int pdev_nr, char *out)
 	}
 
 	hcd = platform_get_drvdata(pdev);
+	if (!hcd)
+		return 0;
+
 	vhci_hcd = hcd_to_vhci_hcd(hcd);
 	vhci = vhci_hcd->vhci;
 
-- 
2.39.5