Linux Kernel Vulnerability in I/O Polling Mechanism

CVE-2026-98821

What is CVE-2026-98821?

A vulnerability exists in the Linux kernel's block device subsystem involving the I/O polling mechanism. This flaw arises from an inconsistency in handling user integrity metadata during polled direct I/O operations. Specifically, the issue is triggered when IOCB_HAS_METADATA is set, leaving the private field of the I/O control block (iocb) as a uio_meta while the polling function, iocb_bio_iopoll(), expects a proper bio structure. This mismatch can lead to a general protection fault due to dereferencing a null pointer, as reported by KASAN. This vulnerability affects systems utilizing io_uring with polling capabilities combined with user metadata on integrity devices.

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