一、漏洞信息
漏洞编号：CVE-2024-26921
漏洞归属组件：kernel
漏洞归属的版本：4.19.140,4.19.194,4.19.90,5.10.0,6.1.0,6.1.14,6.1.19,6.1.5,6.1.6,6.1.8,6.4.0
CVSS V2.0分值：
BaseScore：0.0 Low
Vector：CVSS：2.0/
漏洞简述：
In the Linux kernel, the following vulnerability has been resolved:inet: inet_defrag: prevent sk release while still in useip_local_out() and other functions can pass skb->sk as function argument.If the skb is a fragment and reassembly happens before such function callreturns, the sk must not be released.This affects skb fragments reassembled via netfilter or similarmodules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline.Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ( inet: frag: Always orphan skbs inside ip_defrag() ) [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used.Eric suggested to stash sk in fragment queue and made an initial patch.However there is a problem with this:If skb is refragmented again right after, ip_do_fragment() will copyhead->sk to the new fragments, and sets up destructor to sock_wfree.IOW, we have no choice but to fix up sk_wmem accouting to reflect thefully reassembled skb, else wmem will underflow.This change moves the orphan down into the core, to last possible moment.As ip_defrag_offset is aliased with sk_buff->sk member, we must move theoffset into the FRAG_CB, else skb->sk gets clobbered.This allows to delay the orphaning long enough to learn if the skb hasto be queued or if the skb is completing the reasm queue.In the former case, things work as before, skb is orphaned. This issafe because skb gets queued/stolen and won t continue past reasm engine.In the latter case, we will steal the skb->sk reference, reattach it tothe head skb, and fix up wmem accouting when inet_frag inflates truesize.
漏洞公开时间：2024-04-18 18:15:07
漏洞创建时间：2024-04-18 19:55:35
漏洞详情参考链接：
https://nvd.nist.gov/vuln/detail/CVE-2024-26921

漏洞分析指导链接：
https://gitee.com/openeuler/cve-manager/blob/master/cve-vulner-manager/doc/md/manual.md
漏洞数据来源:
openBrain开源漏洞感知系统
漏洞补丁信息：

二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:inet: inet_defrag: prevent sk release while still in useip_local_out() and other functions can pass skb->sk as function argument.If the skb is a fragment and reassembly happens before such function callreturns, the sk must not be released.This affects skb fragments reassembled via netfilter or similarmodules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline.Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ( inet: frag: Always orphan skbs inside ip_defrag() ) [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used.Eric suggested to stash sk in fragment queue and made an initial patch.However there is a problem with this:If skb is refragmented again right after, ip_do_fragment() will copyhead->sk to the new fragments, and sets up destructor to sock_wfree.IOW, we have no choice but to fix up sk_wmem accouting to reflect thefully reassembled skb, else wmem will underflow.This change moves the orphan down into the core, to last possible moment.As ip_defrag_offset is aliased with sk_buff->sk member, we must move theoffset into the FRAG_CB, else skb->sk gets clobbered.This allows to delay the orphaning long enough to learn if the skb hasto be queued or if the skb is completing the reasm queue.In the former case, things work as before, skb is orphaned. This issafe because skb gets queued/stolen and won t continue past reasm engine.In the latter case, we will steal the skb->sk reference, reattach it tothe head skb, and fix up wmem accouting when inet_frag inflates truesize.
openEuler评分：
7.8
Vector：CVSS：2.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
受影响版本排查(受影响/不受影响)：
1.openEuler-20.03-LTS-SP1(4.19.90):受影响
2.openEuler-20.03-LTS-SP4(4.19.90):受影响
3.openEuler-22.03-LTS(5.10.0):受影响
4.openEuler-22.03-LTS-SP1(5.10.0):受影响
5.openEuler-22.03-LTS-SP2(5.10.0):受影响
6.openEuler-22.03-LTS-SP3(5.10.0):受影响
7.master(6.1.0):不受影响
8.openEuler-22.03-LTS-Next(5.10.0):不受影响
9.openEuler-24.03-LTS:不受影响
10.openEuler-24.03-LTS-Next:不受影响

修复是否涉及abi变化(是/否)：
1.openEuler-20.03-LTS-SP1(4.19.90):否
2.openEuler-20.03-LTS-SP4(4.19.90):否
3.openEuler-22.03-LTS(5.10.0):否
4.openEuler-22.03-LTS-SP1(5.10.0):否
5.openEuler-22.03-LTS-SP2(5.10.0):否
6.openEuler-22.03-LTS-SP3(5.10.0):否
7.master(6.1.0):否
8.openEuler-22.03-LTS-Next(5.10.0):否
9.openEuler-24.03-LTS:否
10.openEuler-24.03-LTS-Next:否