CVE-2026-90051

/// Technical description

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

tcp: reject non zerocopy devmem tx

Devmem tcp tx doesn't work without zero-copy, however it's not currently

enforced if NETIF_F_SG isn't present. In this case, tcp_sendmsg_locked()

will try the copy path and try to copy data from an iovec which consists

of offsets into the dma-buf and would normally fail. Moreover,

d9c56501c72fd ("net: tcp: block mixing readable and unreadable frags")

relies on that and assumes that the devmem binding is present IFF we're

using the zero-copy path, which can be used to mix net-iov and pages in

a single skb, and break invariants. Let's reject devmem tx without

zero-copy.

Note, the parameter check the patch is modifying is too loose, we can

create an io_uring request with dmabuf_id and all ZC flags, but which

won't have the binding. We replace it with stricter validation.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References