CVE-2022-50410

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

NFSD: Protect against send buffer overflow in NFSv2 READ

Since before the git era, NFSD has conserved the number of pages held by each nfsd thread by combining the RPC receive and send buffers into a single array of pages. This works because there are no cases where an operation needs a large RPC Call message and a large RPC Reply at the same time.

Once an RPC Call has been received, svc_process() updates svc_rqst::rq_res to describe the part of rq_pages that can be used for constructing the Reply. This means that the send buffer (rq_res) shrinks when the received RPC record containing the RPC Call is large.

A client can force this shrinkage on TCP by sending a correctly- formed RPC Call header contained in an RPC record that is excessively large. The full maximum payload size cannot be constructed in that case.

A logic flaw in the NFSv2 server implementation could allow a remote NFS client to trigger a send-buffer overflow by sending a valid but excessively large RPC Call header, resulting in an oversized READ request exceeding the available response buffer. Successful exploitation could lead to memory corruption and potential denial of service (kernel crash).

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.