linux-cve-announce - CVE-2022-50506: drbd: only clone bio if we have a backing device

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Message-ID: <2025100422-CVE-2022-50506-1642@gregkh>
Date: Sat,  4 Oct 2025 17:51:31 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50506: drbd: only clone bio if we have a backing device

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

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

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

drbd: only clone bio if we have a backing device

Commit c347a787e34cb (drbd: set ->bi_bdev in drbd_req_new) moved a
bio_set_dev call (which has since been removed) to "earlier", from
drbd_request_prepare to drbd_req_new.

The problem is that this accesses device->ldev->backing_bdev, which is
not NULL-checked at this point. When we don't have an ldev (i.e. when
the DRBD device is diskless), this leads to a null pointer deref.

So, only allocate the private_bio if we actually have a disk. This is
also a small optimization, since we don't clone the bio to only to
immediately free it again in the diskless case.

The Linux kernel CVE team has assigned CVE-2022-50506 to this issue.

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

	Issue introduced in 5.18 with commit c347a787e34cba0e5a80a04082dacaf259105605 and fixed in 6.0.6 with commit 05580a3bbf3cec677cb00a85dfeb21d6a9b48eaf
	Issue introduced in 5.18 with commit c347a787e34cba0e5a80a04082dacaf259105605 and fixed in 6.1 with commit 6d42ddf7f27b6723549ee6d4c8b1b418b59bf6b5

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-2022-50506
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/block/drbd/drbd_req.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/05580a3bbf3cec677cb00a85dfeb21d6a9b48eaf
	https://git.kernel.org/stable/c/6d42ddf7f27b6723549ee6d4c8b1b418b59bf6b5