CVE-2026-64535: nvmet-tcp: Fix potential UAF when ddgst mismatch

CVE-2026-64535: nvmet-tcp: Fix potential UAF when ddgst mismatch

[Greg Kroah-Hartman]

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

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

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

nvmet-tcp: Fix potential UAF when ddgst mismatch

Shivam Kumar found via vulnerability testing:
When data digest is enabled on an NVMe/TCP connection and a digest
mismatch occurs on a non-final H2C_DATA PDU during an R2T-based
data transfer, the digest error handler in nvmet_tcp_try_recv_ddgst()
calls nvmet_req_uninit() — which performs percpu_ref_put() on the
submission queue — but does NOT mark the command as completed. It
does not set cqe->status, does not modify rbytes_done, and does not
clear any flag. When the subsequent fatal error triggers queue
teardown, nvmet_tcp_uninit_data_in_cmds() iterates all commands,
checks nvmet_tcp_need_data_in() for each one, and finds that the
already-uninited command still appears to need data (because
rbytes_done < transfer_len and cqe->status == 0). It therefore calls
nvmet_req_uninit() a second time on the same command — a double
percpu_ref_put against a single percpu_ref_get.

The Linux kernel CVE team has assigned CVE-2026-64535 to this issue.


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

	Fixed in 6.1.178 with commit 96fe2513df590e74b04253a45089cae75569570e
	Fixed in 6.6.145 with commit e091ff83d962f9ed00d9bd70443676de9fe98bdc
	Fixed in 6.12.97 with commit 6f9442983a3e4227afd1c83a5251ddbca585ea21
	Fixed in 6.18.40 with commit 088ee46c18d99baef453afd74181dd40ade044ad
	Fixed in 7.1 with commit dbbd07d0a7020b80f6a7028e561908f7b83b3d5a

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-2026-64535
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/target/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/96fe2513df590e74b04253a45089cae75569570e
	https://git.kernel.org/stable/c/e091ff83d962f9ed00d9bd70443676de9fe98bdc
	https://git.kernel.org/stable/c/6f9442983a3e4227afd1c83a5251ddbca585ea21
	https://git.kernel.org/stable/c/088ee46c18d99baef453afd74181dd40ade044ad
	https://git.kernel.org/stable/c/dbbd07d0a7020b80f6a7028e561908f7b83b3d5a