CVE-2026-52954: libceph: handle rbtree insertion error in decode_choose_args()

CVE-2026-52954: libceph: handle rbtree insertion error in decode_choose_args()

[Greg Kroah-Hartman]

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

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

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

libceph: handle rbtree insertion error in decode_choose_args()

A message of type CEPH_MSG_OSD_MAP contains an OSD map that itself
contains a CRUSH map. The received CRUSH map may optionally contain
choose_args that get decoded in decode_choose_args(). In this function,
num_choose_arg_maps is read from the message, and a corresponding number
of crush_choose_arg_maps gets decoded afterwards. Each
crush_choose_arg_map has a choose_args_index, which serves as the key
when inserting it into the choose_args rbtree of the decoded crush_map.
If a (potentially corrupted) message contains two crush_choose_arg_maps
with the same index, the assertion in insert_choose_arg_map() triggers a
kernel BUG when trying to insert the second crush_choose_arg_map.

This patch fixes the issue by switching to the non-asserting rbtree
insertion function and rejecting the message if the insertion fails.

[ idryomov: changelog ]

The Linux kernel CVE team has assigned CVE-2026-52954 to this issue.


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

	Fixed in 5.10.258 with commit c7bf7864e2924fa5508ac270b0e9364bc13d5a6c
	Fixed in 5.15.209 with commit f47430fc1f815e87406e2d3b4e476eff1bc7fd9b
	Fixed in 6.1.175 with commit 0b6a3bcb91bc5bfeda39f0df3b71bab62c13e9da
	Fixed in 6.6.141 with commit 534ebc08df97c47d4c7596f336fa31ecbf91519c
	Fixed in 6.12.91 with commit 80c73bd1b2b04355d1d0c29be8ccbd25a380905d
	Fixed in 6.18.33 with commit 4d2b37abda9536808655830d683dc491d31741a8
	Fixed in 7.0.10 with commit 0a1265a9ab875f92b6a3ffb497404f46cf9d76a3
	Fixed in 7.1 with commit d289478cfc0bcf81c7914200d6abdcb78bd04ded

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-2026-52954
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:
	net/ceph/osdmap.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/c7bf7864e2924fa5508ac270b0e9364bc13d5a6c
	https://git.kernel.org/stable/c/f47430fc1f815e87406e2d3b4e476eff1bc7fd9b
	https://git.kernel.org/stable/c/0b6a3bcb91bc5bfeda39f0df3b71bab62c13e9da
	https://git.kernel.org/stable/c/534ebc08df97c47d4c7596f336fa31ecbf91519c
	https://git.kernel.org/stable/c/80c73bd1b2b04355d1d0c29be8ccbd25a380905d
	https://git.kernel.org/stable/c/4d2b37abda9536808655830d683dc491d31741a8
	https://git.kernel.org/stable/c/0a1265a9ab875f92b6a3ffb497404f46cf9d76a3
	https://git.kernel.org/stable/c/d289478cfc0bcf81c7914200d6abdcb78bd04ded