linux-cve-announce - CVE-2022-50728: s390/lcs: Fix return type of lcs_start

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Message-ID: <2025122419-CVE-2022-50728-afa8@gregkh>
Date: Wed, 24 Dec 2025 13:26:27 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50728: s390/lcs: Fix return type of lcs_start_xmit()

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

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

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

s390/lcs: Fix return type of lcs_start_xmit()

With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function
pointer prototype to make sure the call target is valid to help mitigate
ROP attacks. If they are not identical, there is a failure at run time,
which manifests as either a kernel panic or thread getting killed. A
proposed warning in clang aims to catch these at compile time, which
reveals:

  drivers/s390/net/lcs.c:2090:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict]
          .ndo_start_xmit         = lcs_start_xmit,
                                    ^~~~~~~~~~~~~~
  drivers/s390/net/lcs.c:2097:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict]
          .ndo_start_xmit         = lcs_start_xmit,
                                    ^~~~~~~~~~~~~~

->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
'netdev_tx_t', not 'int'. Adjust the return type of lcs_start_xmit() to
match the prototype's to resolve the warning and potential CFI failure,
should s390 select ARCH_SUPPORTS_CFI_CLANG in the future.

The Linux kernel CVE team has assigned CVE-2022-50728 to this issue.


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

	Fixed in 4.9.337 with commit 7b4da3fcd513b8e67823eb80da37aad99b3339c1
	Fixed in 4.14.303 with commit d49cc2b705711fb8fb849e7c660929b2100360b7
	Fixed in 4.19.270 with commit e684215d8a903752e2b0cc946517fb61e57a880a
	Fixed in 5.4.229 with commit 20022d551f2064a194d8e0acb6cd7a85094a17b2
	Fixed in 5.10.163 with commit ebc3c77785dc8b5b626309c0032a38fbb139287a
	Fixed in 5.15.86 with commit 5ad774fb823c24bbeb21a15a67103ea7a6f5b928
	Fixed in 6.0.16 with commit 69669820844f81a77b6db24b86581320ae4d17af
	Fixed in 6.1.2 with commit cda74cdc280ba35c8993e7517bac5c257ff36f18
	Fixed in 6.2 with commit bb16db8393658e0978c3f0d30ae069e878264fa3

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-2022-50728
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/s390/net/lcs.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/7b4da3fcd513b8e67823eb80da37aad99b3339c1
	https://git.kernel.org/stable/c/d49cc2b705711fb8fb849e7c660929b2100360b7
	https://git.kernel.org/stable/c/e684215d8a903752e2b0cc946517fb61e57a880a
	https://git.kernel.org/stable/c/20022d551f2064a194d8e0acb6cd7a85094a17b2
	https://git.kernel.org/stable/c/ebc3c77785dc8b5b626309c0032a38fbb139287a
	https://git.kernel.org/stable/c/5ad774fb823c24bbeb21a15a67103ea7a6f5b928
	https://git.kernel.org/stable/c/69669820844f81a77b6db24b86581320ae4d17af
	https://git.kernel.org/stable/c/cda74cdc280ba35c8993e7517bac5c257ff36f18
	https://git.kernel.org/stable/c/bb16db8393658e0978c3f0d30ae069e878264fa3