tree 0a4a5bb0cc23289a8307a6401ff3bf0f92bbba61
parent b0f61c19b0f70b3abb9a2bc3092d0f9f8281f55d
author Chuck Lever <chuck.lever@oracle.com> 1662059418 -0400
committer Oleksandr Tymoshenko <ovt@google.com> 1668045546 +0000

NFSD: Protect against send buffer overflow in NFSv2 READ

commit 401bc1f90874280a80b93f23be33a0e7e2d1f912 upstream.

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.

BUG=b/258184692
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2022-43945 in the Linux kernel.

cos-patch: security-high
Cc: <stable@vger.kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I56fa2412fc352459a23cae0563a94ce18028591d
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/38494
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Meena Shanmugam <meenashanmugam@google.com>