CVE-2026-89480: nvme-tcp: reject a read that transferred too few bytes

CVE-2026-89480: nvme-tcp: reject a read that transferred too few bytes

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

nvme-tcp: reject a read that transferred too few bytes

nvme_tcp_recv_data() completes a request once the current C2HData PDU
has been consumed. Nothing compares the total bytes received against
the length the command asked for: struct nvme_tcp_request has no
receive-side counter, queue->data_remaining is per queue, and
blk_mq_end_request() completes for blk_rq_bytes(rq) unconditionally
with no residual concept anywhere above.

A controller can therefore answer a 4096-byte read with 512 bytes and
have it reported as a complete read; user space then gets 4096 bytes of
which 3584 are whatever was already in the page. I reproduced that with
a test target.

Count the bytes received and refuse to complete a successful read whose
count does not match, at the two NVME_TCP_F_DATA_SUCCESS paths and in
nvme_tcp_process_nvme_cqe(). The success test shifts req->status right
by one, because the driver keeps the wire value there and shifts it on
completion, so the check must see what the completion path will see.
Only REQ_OP_READ is checked, because there the length comes from the
sectors the request covers; a passthrough command is built by its
submitter, which picks both command and buffer, so the kernel has
nothing to compare against.

The Linux kernel CVE team has assigned CVE-2026-89480 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.0 with commit 3f2304f8c6d6ed97849057bd16fee99e434ca796 and fixed in 6.12.109 with commit 99066cf9bba175f610ceb61a35f6fc9fbc33ff65
	Issue introduced in 5.0 with commit 3f2304f8c6d6ed97849057bd16fee99e434ca796 and fixed in 6.18.50 with commit 8a02ad98798fd01f51f648c1fdd8f3c9d07195d3
	Issue introduced in 5.0 with commit 3f2304f8c6d6ed97849057bd16fee99e434ca796 and fixed in 7.2.4 with commit 832a685efeb5d925ee7d30011d2dbe45f81447a3
	Issue introduced in 5.0 with commit 3f2304f8c6d6ed97849057bd16fee99e434ca796 and fixed in 7.3-rc1 with commit 7fa3f73f6c8ddc5f0425b50fb2a626a782ef7d12

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89480
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/nvme/host/tcp.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/99066cf9bba175f610ceb61a35f6fc9fbc33ff65
	https://git.kernel.org/stable/c/8a02ad98798fd01f51f648c1fdd8f3c9d07195d3
	https://git.kernel.org/stable/c/832a685efeb5d925ee7d30011d2dbe45f81447a3
	https://git.kernel.org/stable/c/7fa3f73f6c8ddc5f0425b50fb2a626a782ef7d12