CVE-2026-63894: In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: serialize DMABUF cancel against request completion ffs_epfile_dmabuf

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: serialize DMABUF cancel against request completion ffs_epfile_dmabuf_io

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: serialize DMABUF cancel against request completion ffs_epfile_dmabuf_io_complete() calls usb_ep_free_request() on the completed request but leaves priv->req, the back-pointer that ffs_dmabuf_transfer() set on submission, pointing at the freed memory. A later FUNCTIONFS_DMABUF_DETACH ioctl or ffs_epfile_release() on the close path still sees priv->req non-NULL under ffs->eps_lock: if (priv->ep && priv->req) usb_ep_dequeue(priv->ep, priv->req); so usb_ep_dequeue() is called on a freed usb_request. On dummy_hcd the dequeue path only walks a live queue and pointer-compares, so the freed pointer reads without faulting and KASAN requires an explicit check at the FunctionFS call site to surface the use-after-free. On SG-capable in-tree UDCs the dequeue path dereferences the supplied request immediately: * chipidea's ep_dequeue() does container_of(req, struct ci_hw_req, req) and reads hwreq->req.status before acquiring its own lock. * cdnsp's cdnsp_gadget_ep_dequeue() reads request->status first. The narrower option of clearing priv->req via cmpxchg() in the completio

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.17%, higher than 6% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

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Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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