CVE-2026-90104: NFSv4.1: zero referring call lists before decoding

CVE-2026-90104: NFSv4.1: zero referring call lists before decoding

[Greg Kroah-Hartman]

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

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

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

NFSv4.1: zero referring call lists before decoding

decode_cb_sequence_args() allocates csa_rclists with kmalloc_objs(), so
each referring_call_list starts uninitialized. decode_rc_list() assigns
rcl_refcalls only when rcl_nrefcalls is nonzero. A valid list with zero
referring calls therefore leaves the pointer uninitialized, and
nfs4_callback_sequence() later passes stale slab contents to kfree().

Allocate csa_rclists with kzalloc_objs() so every rcl_refcalls member is
NULL from the beginning, including valid empty referring call lists.

The Linux kernel CVE team has assigned CVE-2026-90104 to this issue.


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

	Issue introduced in 2.6.31 with commit 4aece6a19cf7f474f15eb861ba74db4479884ce3 and fixed in 7.2.6 with commit f31f3c042e024aef437cda42f0424ae8d4594b6c
	Issue introduced in 2.6.31 with commit 4aece6a19cf7f474f15eb861ba74db4479884ce3 and fixed in 7.3-rc1 with commit 8fa4804fe62ca4155a2d8fc2789d630376cbf2fc

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-2026-90104
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:
	fs/nfs/callback_xdr.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/f31f3c042e024aef437cda42f0424ae8d4594b6c
	https://git.kernel.org/stable/c/8fa4804fe62ca4155a2d8fc2789d630376cbf2fc