[LTS 8.6] nvme-tcp: fix potential memory corruption in nvme_tcp_recv_pdu()

[pvts-mat]

[LTS 8.6]
CVE-2025-21927
VULN-56023

Problem

https://www.cve.org/CVERecord?id=CVE-2025-21927

In the Linux kernel, the following vulnerability has been resolved: nvme-tcp: fix potential memory corruption in nvme_tcp_recv_pdu() nvme_tcp_recv_pdu() doesn't check the validity of the header length. When header digests are enabled, a target might send a packet with an invalid header length (e.g. 255), causing nvme_tcp_verify_hdgst() to access memory outside the allocated area and cause memory corruptions by overwriting it with the calculated digest. Fix this by rejecting packets with an unexpected header length.

Analysis and Solution (same as for ciqlts8_8)

Context

NVME (Non-Volatile Memory Express) is a communication protocol designed for accessing high-speed storage media, particularly solid-state drives (SSDs). NVMe over Fabrics (NVMe-oF) is an extension of the NVMe protocol that allows NVMe commands to be sent over a network fabric, enabling remote access to NVMe storage devices.

The "target" mentioned in CVE description is the host providing access to the local NVME device (the server). The host importing the remote NVME device is called simply a "host", or "initiator" (the client). The module implementing NVMe-oF on target's side is nvmet-tcp, on the initiator's side it's nvme-tcp - the subject of this patch.

Applicability

All the key options related to NVMe-oF, specifically CONFIG_NVME_TCP enabling the nvme-tcp module, are enabled in ciqlts8_6. Per .config file created from configs/kernel-x86_64.config:

#
# NVME Support
#
CONFIG_NVME_CORE=m
CONFIG_BLK_DEV_NVME=m
CONFIG_NVME_MULTIPATH=y
# CONFIG_NVME_HWMON is not set
CONFIG_NVME_FABRICS=m
CONFIG_NVME_RDMA=m
CONFIG_NVME_FC=m
CONFIG_NVME_TCP=m
CONFIG_NVME_TARGET=m
# CONFIG_NVME_TARGET_PASSTHRU is not set
CONFIG_NVME_TARGET_LOOP=m
CONFIG_NVME_TARGET_RDMA=m
CONFIG_NVME_TARGET_FC=m
CONFIG_NVME_TARGET_FCLOOP=m
CONFIG_NVME_TARGET_TCP=m

Solution

The solution in the mainline kernel is provided in the ad95bab commit. It was not backported to any stable kernel older than 6.12.

Naive cherry-picking results in conflicts with git's attempt to introduce additional functions (nvme_tcp_tls_configured, nvme_tcp_queue_tls) and code branches (nvme_tcp_c2h_term packet type check in the nvme_tcp_recv_pdu function) introduced in more recent versions of the module but not related to the bug fix.

A small change was made to the nvme_tcp_recv_pdu_supported function introduced in the official fix ad95bab for the sake of nvme_tcp_recv_pdu's behavior consistency between the scenarios of receiving a packet with a proper and an improper header - the removal of the nvme_tcp_c2h_term case.

Consider the behavior cases in case a packet with a proper header was received:

	Packet type:	X ∈ {c2h_term}	X ∈ {c2h_data, rsp, r2t}	X ∉ {c2h_term, c2h_data, rsp, r2t}
a	Mainline, after patch (ad95bab)	nvme_tcp_handle_X	nvme_tcp_handle_X	"unsupported pdu type …", -EINVAL
b	ciqlts8_6, after patch, c2h_term included	"unsupported pdu type …", -EINVAL	nvme_tcp_handle_X	"unsupported pdu type …", -EINVAL
c	ciqlts8_6, after patch, c2h_term excluded	"unsupported pdu type …", -EINVAL	nvme_tcp_handle_X	"unsupported pdu type …", -EINVAL

Then in case a packet with an improper header was received:

	Packet type:	X ∈ {c2h_term}	X ∈ {c2h_data, rsp, r2t}	X ∉ {c2h_term, c2h_data, rsp, r2t}
x	Mainline, after patch (ad95bab)	"pdu type %d has unexpected header length", -EPROTO	"pdu type %d has unexpected header length", -EPROTO	"unsupported pdu type …", -EINVAL
y	ciqlts8_6, after patch, c2h_term included	"pdu type %d has unexpected header length", -EPROTO	"pdu type %d has unexpected header length", -EPROTO	"unsupported pdu type …", -EINVAL
z	ciqlts8_6, after patch, c2h_term excluded	"unsupported pdu type …", -EINVAL	"pdu type %d has unexpected header length", -EPROTO	"unsupported pdu type …", -EINVAL

Solution a is to xnot as b is to y, but as c is to z, thus the c, z pair was chosen.

kABI check: passed

DEBUG=1 RELAXED_DEPS=1 CVE=CVE-2025-21927 ./ninja.sh _kabi_checked__x86_64--test--ciqlts8_6-CVE-2025-21927
[0/1] Check ABI of kernel [ciqlts8_6-CVE-2025-21927]
++ uname -m
+ python3 /data/src/ctrliq-github/kernel-dist-git-el-8.6/SOURCES/check-kabi -k /data/src/ctrliq-github/kernel-dist-git-el-8.6/SOURCES/Module.kabi_x86_64 -s vms/x86_64--build--ciqlts8_6/build_files/kernel-src-tree-ciqlts8_6-CVE-2025-21927/Module.symvers
kABI check passed
+ touch state/kernels/ciqlts8_6-CVE-2025-21927/x86_64/kabi_checked

Boot test: passed

boot-test.log

Kselftests

Methodology

The selftests were source-compiled from the recent ciqlts8_6 branch (commit 00366e2).

The tests were run using an explicit list which omitted certain tests known to give inconsistent results. Details in the src/run-kselftests.sh script of the rocky-patching project.

Coverage

android, bpf (except test_kmod.sh, test_progs, test_progs-no_alu32, test_sockmap, test_xsk.sh), breakpoints, capabilities, core, cpu-hotplug, cpufreq, efivarfs, exec, firmware, fpu, ftrace, futex, gpio, intel_pstate, ipc, kcmp, kexec, kvm, lib, livepatch, membarrier, memfd, memory-hotplug, mount, net (except gro.sh, ip_defrag.sh, reuseaddr_conflict, txtimestamp.sh, udpgso_bench.sh), net/forwarding (except ipip_hier_gre_keys.sh, sch_ets.sh, sch_tbf_ets.sh, sch_tbf_prio.sh, sch_tbf_root.sh, tc_actions.sh), net/mptcp, netfilter (except nft_trans_stress.sh), nsfs, proc, pstore, ptrace, rseq, sgx, sigaltstack, size, splice, static_keys, sync, sysctl, tc-testing, timens, timers (except raw_skew), tpm2, user, vm, x86, zram.

Reference

The results are provided in two parts, because the first batch run was ending prematurely and missing around 1/3 of tests.

kselftests–ciqlts8_6–part1–run1.log
kselftests–ciqlts8_6–part1–run2.log
kselftests–ciqlts8_6–part1–run3.log
kselftests–ciqlts8_6–part2–run1.log
kselftests–ciqlts8_6–part2–run2.log
kselftests–ciqlts8_6–part2–run3.log

Patch

The results are provided in two parts, because the first batch run was ending prematurely and missing around 1/3 of tests.

kselftests–ciqlts8_6-CVE-2025-21927–part1–run1.log
kselftests–ciqlts8_6-CVE-2025-21927–part2–run1.log

Comparison

The results are the same in the reference and patched kernel.

./ktests.xsh diff -d kselftests*.log
Column File
-------- -----------------------------------------------------
Status0 kselftests--ciqlts8_6--part1--run1.log
Status1 kselftests--ciqlts8_6--part1--run2.log
Status2 kselftests--ciqlts8_6--part1--run3.log
Status3 kselftests--ciqlts8_6--part2--run1.log
Status4 kselftests--ciqlts8_6--part2--run2.log
Status5 kselftests--ciqlts8_6--part2--run3.log
Status6 kselftests--ciqlts8_6-CVE-2025-21927--part1--run1.log
Status7 kselftests--ciqlts8_6-CVE-2025-21927--part2--run1.log

Specific tests: suspended

See the situation for #234.

[bmastbergen]

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