[fips-legacy-8] net/sched: sch_qfq: account for stab overhead in qfq_enqueue

[bmastbergen]

jira VULN-8822
cve CVE-2023-3611

commit-author Pedro Tammela <pctammela@mojatatu.com> commit 3e337087c3b5805fe0b8a46ba622a962880b5d64
upstream-diff used linux-stable LT-4.19 sha ee3bc829f9b4df96d208d58b654e400fa1f3b46c

commit 3e337087c3b5805fe0b8a46ba622a962880b5d64 upstream.

Lion says:
-------
In the QFQ scheduler a similar issue to CVE-2023-31436 persists.

Consider the following code in net/sched/sch_qfq.c:

static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                struct sk_buff **to_free)
{
     unsigned int len = qdisc_pkt_len(skb), gso_segs;

    // ...

     if (unlikely(cl->agg->lmax < len)) {
         pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
              cl->agg->lmax, len, cl->common.classid);
         err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
         if (err) {
             cl->qstats.drops++;
             return qdisc_drop(skb, sch, to_free);
         }

    // ...

     }

Similarly to CVE-2023-31436, "lmax" is increased without any bounds checks according to the packet length "len". Usually this would not impose a problem because packet sizes are naturally limited.

This is however not the actual packet length, rather the "qdisc_pkt_len(skb)" which might apply size transformations according to "struct qdisc_size_table" as created by "qdisc_get_stab()" in net/sched/sch_api.c if the TCA_STAB option was set when modifying the qdisc.

A user may choose virtually any size using such a table.

As a result the same issue as in CVE-2023-31436 can occur, allowing heap out-of-bounds read / writes in the kmalloc-8192 cache. -------

We can create the issue with the following commands:

tc qdisc add dev $DEV root handle 1: stab mtu 2048 tsize 512 mpu 0 \ overhead 999999999 linklayer ethernet qfq
tc class add dev $DEV parent 1: classid 1:1 htb rate 6mbit burst 15k tc filter add dev $DEV parent 1: matchall classid 1:1 ping -I $DEV 1.1.1.2

This is caused by incorrectly assuming that qdisc_pkt_len() returns a length within the QFQ_MIN_LMAX < len < QFQ_MAX_LMAX.

Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost")
	Reported-by: Lion <nnamrec@gmail.com>
	Reviewed-by: Eric Dumazet <edumazet@google.com>
	Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
	Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
	Reviewed-by: Simon Horman <simon.horman@corigine.com>
	Signed-off-by: Paolo Abeni <pabeni@redhat.com>
	Signed-off-by: Shaoying Xu <shaoyi@amazon.com>
	Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit ee3bc829f9b4df96d208d58b654e400fa1f3b46c)
	Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>

Build Log

/home/brett/kernel-src-tree
no .config file found, moving on
[TIMER]{MRPROPER}: 0s
x86_64 architecture detected, copying config
'configs/kernel-x86_64.config' -> '.config'
Setting Local Version for build
CONFIG_LOCALVERSION="-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b"
Making olddefconfig
--
  HOSTLD  scripts/kconfig/conf
scripts/kconfig/conf  --olddefconfig Kconfig
#
# configuration written to .config
#
Starting Build
scripts/kconfig/conf  --syncconfig Kconfig
  SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
  SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
--
  LD [M]  sound/usb/usx2y/snd-usb-usx2y.ko
  LD [M]  sound/x86/snd-hdmi-lpe-audio.ko
  LD [M]  sound/xen/snd_xen_front.ko
  LD [M]  sound/virtio/virtio_snd.ko
  LD [M]  virt/lib/irqbypass.ko
[TIMER]{BUILD}: 1019s
Making Modules
  INSTALL arch/x86/crypto/blowfish-x86_64.ko
  INSTALL arch/x86/crypto/camellia-aesni-avx-x86_64.ko
  INSTALL arch/x86/crypto/camellia-aesni-avx2.ko
  INSTALL arch/x86/crypto/camellia-x86_64.ko
--
  INSTALL sound/virtio/virtio_snd.ko
  INSTALL sound/x86/snd-hdmi-lpe-audio.ko
  INSTALL sound/xen/snd_xen_front.ko
  INSTALL virt/lib/irqbypass.ko
  DEPMOD  4.18.0-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b+
[TIMER]{MODULES}: 13s
Making Install
sh ./arch/x86/boot/install.sh 4.18.0-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b+ arch/x86/boot/bzImage \
	System.map "/boot"
[TIMER]{INSTALL}: 62s
Checking kABI
Checking kABI
kABI check passed
Setting Default Kernel to /boot/vmlinuz-4.18.0-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b+ and Index to 0
Hopefully Grub2.0 took everything ... rebooting after time metrices
[TIMER]{MRPROPER}: 0s
[TIMER]{BUILD}: 1019s
[TIMER]{MODULES}: 13s
[TIMER]{INSTALL}: 62s
[TIMER]{TOTAL} 1109s
Rebooting in 10 seconds

Testing

kselftests were run before and after applying the change

selftest-4.18.0-425.13.1.el8.ciqfipscompliant.39.1.x86_64.log

selftest-4.18.0-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b+.log

brett@lycia ~/ciq/vuln-8822 % grep ^ok selftest-4.18.0-425.13.1.el8.ciqfipscompliant.39.1.x86_64.log | wc -l
229
brett@lycia ~/ciq/vuln-8822 % grep ^ok selftest-4.18.0-b_f-l-8-c_4.18.0-425.13.1_VULN-8822-bb3f6e35c82b+.log | wc -l
227
brett@lycia ~/ciq/vuln-8822 %

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