CVE-2022-48644

What it is

In the Linux kernel, the following vulnerability has been resolved: net/sched: taprio: avoid disabling offload when it was never enabled In an incredibly strange API design decision, qdisc->destroy() gets called even if qdisc->init() never succeeded, not exclusively since commit 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation"), but apparently also earlier (in the case of qdisc_create_dflt()). The taprio qdisc does not fully acknowledge this when it attempts full offload, because it starts off with q->flags = TAPRIO_FLAGS_INVALID in taprio_init(), then it replaces q->flags with TCA_TAPRIO_ATTR_FLAGS parsed from netlink (in taprio_change(), tail called from taprio_init()). But in taprio_destroy(), we call taprio_disable_offload(), and this determines what to do based on FULL_OFFLOAD_IS_ENABLED(q->flags). But looking at the implementation of FULL_OFFLOAD_IS_ENABLED() (a bitwise check of bit 1 in q->flags), it is invalid to call this macro on q->flags when it contains TAPRIO_FLAGS_INVALID, because that is set to U32_MAX, and therefore FULL_OFFLOAD_IS_ENABLED() will return true on an invalid set of flags. As a result, it is possible to crash the kernel if user space forces an error between setting q->flags = TAPRIO_FLAGS_INVALID, and the calling of taprio_enable_offload(). This is because drivers do not expect the offload to be disabled when it was never enabled. The error that we force here is to attach taprio as a non-root qdisc, but instead as child of an mqprio root qdisc: $ tc qdisc add dev swp0 root handle 1: \ mqprio num_tc 8 map 0 1 2 3 4 5 6 7 \ queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 hw 0 $ tc qdisc replace dev swp0 parent 1:1 \ taprio num_tc 8 map 0 1 2 3 4 5 6 7 \ queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 0 \ sched-entry S 0x7f 990000 sched-entry S 0x80 100000 \ flags 0x0 clockid CLOCK_TAI Unable to handle kernel paging request at virtual address fffffffffffffff8 [fffffffffffffff8] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 96000004 [#1] PREEMPT SMP Call trace: taprio_dump+0x27c/0x310 vsc9959_port_setup_tc+0x1f4/0x460 felix_port_setup_tc+0x24/0x3c dsa_slave_setup_tc+0x54/0x27c taprio_disable_offload.isra.0+0x58/0xe0 taprio_destroy+0x80/0x104 qdisc_create+0x240/0x470 tc_modify_qdisc+0x1fc/0x6b0 rtnetlink_rcv_msg+0x12c/0x390 netlink_rcv_skb+0x5c/0x130 rtnetlink_rcv+0x1c/0x2c Fix this by keeping track of the operations we made, and undo the offload only if we actually did it. I've added "bool offloaded" inside a 4 byte hole between "int clockid" and "atomic64_t picos_per_byte". Now the first cache line looks like below: $ pahole -C taprio_sched net/sched/sch_taprio.o struct taprio_sched { struct Qdisc * * qdiscs; /* 0 8 */ struct Qdisc * root; /* 8 8 */ u32 flags; /* 16 4 */ enum tk_offsets tk_offset; /* 20 4 */ int clockid; /* 24 4 */ bool offloaded; /* 28 1 */ /* XXX 3 bytes hole, try to pack */ atomic64_t picos_per_byte; /* 32 0 */ /* XXX 8 bytes hole, try to pack */ spinlock_t current_entry_lock; /* 40 0 */ /* XXX 8 bytes hole, try to pack */ struct sched_entry * current_entry; /* 48 8 */ struct sched_gate_list * oper_sched; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2024-04-28 13:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 05:15 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 5.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2024-04-28 13:15 UTC

Last modified

2026-06-17 05:15 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Analyzed

Affected

• Linux Kernel < 5.4.215
• Linux Kernel < 5.10.146
• Linux Kernel < 5.15.71
• Linux Kernel < 5.19.12
• Linux Kernel 6.0

Attack profile CVSS 3.1 · 5.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2022-48644.md and follow it. Check whether this project is affected by CVE-2022-48644. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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