Vulnerability CVE-2023-52855
Published: 2024-05-21

Description:
In the Linux kernel, the following vulnerability has been resolved:

usb: dwc2: fix possible NULL pointer dereference caused by driver concurrency

In _dwc2_hcd_urb_enqueue(), "urb->hcpriv = NULL" is executed without
holding the lock "hsotg->lock". In _dwc2_hcd_urb_dequeue():

spin_lock_irqsave(&hsotg->lock, flags);
...
if (!urb->hcpriv) {
dev_dbg(hsotg->dev, "## urb->hcpriv is NULL ##\n");
goto out;
}
rc = dwc2_hcd_urb_dequeue(hsotg, urb->hcpriv); // Use urb->hcpriv
...
out:
spin_unlock_irqrestore(&hsotg->lock, flags);

When _dwc2_hcd_urb_enqueue() and _dwc2_hcd_urb_dequeue() are
concurrently executed, the NULL check of "urb->hcpriv" can be executed
before "urb->hcpriv = NULL". After urb->hcpriv is NULL, it can be used
in the function call to dwc2_hcd_urb_dequeue(), which can cause a NULL
pointer dereference.

This possible bug is found by an experimental static analysis tool
developed by myself. This tool analyzes the locking APIs to extract
function pairs that can be concurrently executed, and then analyzes the
instructions in the paired functions to identify possible concurrency
bugs including data races and atomicity violations. The above possible
bug is reported, when my tool analyzes the source code of Linux 6.5.

To fix this possible bug, "urb->hcpriv = NULL" should be executed with
holding the lock "hsotg->lock". After using this patch, my tool never
reports the possible bug, with the kernelconfiguration allyesconfig for
x86_64. Because I have no associated hardware, I cannot test the patch
in runtime testing, and just verify it according to the code logic.

 References:
https://git.kernel.org/stable/c/14c9ec34e8118fbffd7f5431814d767726323e72
https://git.kernel.org/stable/c/fed492aa6493a91a77ebd51da6fb939c98d94a0d
https://git.kernel.org/stable/c/64c47749fc7507ed732e155c958253968c1d275e
https://git.kernel.org/stable/c/bdb3dd4096302d6b87441fdc528439f171b04be6
https://git.kernel.org/stable/c/fcaafb574fc88a52dce817f039f7ff2f9da38001
https://git.kernel.org/stable/c/6b21a22728852d020a6658d39cd7bb7e14b07790
https://git.kernel.org/stable/c/3e851a77a13ce944d703721793f49ee82622986d
https://git.kernel.org/stable/c/a7bee9598afb38004841a41dd8fe68c1faff4e90
https://git.kernel.org/stable/c/ef307bc6ef04e8c1ea843231db58e3afaafa9fa6
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