linux-cve-announce - CVE-2024-50018: net: napi: Prevent overflow of napi_defer_hard

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Message-ID: <2024102111-CVE-2024-50018-65e9@gregkh>
Date: Mon, 21 Oct 2024 20:54:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50018: net: napi: Prevent overflow of napi_defer_hard_irqs

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

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

net: napi: Prevent overflow of napi_defer_hard_irqs

In commit 6f8b12d661d0 ("net: napi: add hard irqs deferral feature")
napi_defer_irqs was added to net_device and napi_defer_irqs_count was
added to napi_struct, both as type int.

This value never goes below zero, so there is not reason for it to be a
signed int. Change the type for both from int to u32, and add an
overflow check to sysfs to limit the value to S32_MAX.

The limit of S32_MAX was chosen because the practical limit before this
patch was S32_MAX (anything larger was an overflow) and thus there are
no behavioral changes introduced. If the extra bit is needed in the
future, the limit can be raised.

Before this patch:

$ sudo bash -c 'echo 2147483649 > /sys/class/net/eth4/napi_defer_hard_irqs'
$ cat /sys/class/net/eth4/napi_defer_hard_irqs
-2147483647

After this patch:

$ sudo bash -c 'echo 2147483649 > /sys/class/net/eth4/napi_defer_hard_irqs'
bash: line 0: echo: write error: Numerical result out of range

Similarly, /sys/class/net/XXXXX/tx_queue_len is defined as unsigned:

include/linux/netdevice.h:      unsigned int            tx_queue_len;

And has an overflow check:

dev_change_tx_queue_len(..., unsigned long new_len):

  if (new_len != (unsigned int)new_len)
          return -ERANGE;

The Linux kernel CVE team has assigned CVE-2024-50018 to this issue.

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

	Fixed in 6.10.14 with commit d694ad8b7e50
	Fixed in 6.11.3 with commit 5e753b743d3b
	Fixed in 6.12-rc1 with commit 08062af0a521

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-2024-50018
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:
	Documentation/networking/net_cachelines/net_device.rst
	include/linux/netdevice.h
	net/core/net-sysfs.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/d694ad8b7e5004df86ecd415cb2320d543723672
	https://git.kernel.org/stable/c/5e753b743d3b38a3e10be666c32c5434423d0093
	https://git.kernel.org/stable/c/08062af0a52107a243f7608fd972edb54ca5b7f8