patch "usb: cdnsp: Fix a NULL pointer dereference in cdnsp_endpoint_init()" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: cdnsp: Fix a NULL pointer dereference in cdnsp_endpoint_init()

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 37307f7020ab38dde0892a578249bf63d00bca64 Mon Sep 17 00:00:00 2001
From: Zhou Qingyang <[email protected]>
Date: Wed, 1 Dec 2021 01:27:00 +0800
Subject: usb: cdnsp: Fix a NULL pointer dereference in cdnsp_endpoint_init()

In cdnsp_endpoint_init(), cdnsp_ring_alloc() is assigned to pep->ring and there is a dereference of it in cdnsp_endpoint_init(), which could lead to a NULL pointer dereference on failure of cdnsp_ring_alloc().

Fix this bug by adding a check of pep->ring.

This bug was found by a static analyzer. The analysis employs differential checking to identify inconsistent security operations (e.g., checks or kfrees) between two code paths and confirms that the inconsistent operations are not recovered in the current function or the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false positive or hard to trigger. Multiple researchers have cross-reviewed the bug.

Builds with CONFIG_USB_CDNSP_GADGET=y show no new warnings, and our static analyzer no longer warns about this code.

---
 drivers/usb/cdns3/cdnsp-mem.c | 3 +++
 1 file changed, 3 insertions(+)

index ad9aee3f1e39..97866bfb2da9 100644
@@ -987,6 +987,9 @@ int cdnsp_endpoint_init(struct cdnsp_device *pdev,
 
 	/* Set up the endpoint ring. */
 	pep->ring = cdnsp_ring_alloc(pdev, 2, ring_type, max_packet, mem_flags);
+	if (!pep->ring)
+		return -ENOMEM;
+
 	pep->skip = false;
 
 	/* Fill the endpoint context */

2.34.1