CVE-2024-27415

一、漏洞信息
 漏洞编号：[CVE-2024-27415](https://nvd.nist.gov/vuln/detail/CVE-2024-27415)
 漏洞归属组件：[kernel](https://gitee.com/src-openeuler/kernel)
 漏洞归属的版本：4.19.140,4.19.194,4.19.90,5.10.0,6.1.0,6.1.14,6.1.19,6.1.5,6.1.6,6.1.8,6.4.0,6.6.0
 CVSS V3.0分值：
  BaseScore：0.0 None
  Vector：CVSS：3.0/
 漏洞简述：
  In the Linux kernel, the following vulnerability has been resolved:netfilter: bridge: confirm multicast packets before passing them up the stackconntrack nf_confirm logic cannot handle cloned skbs referencingthe same nf_conn entry, which will happen for multicast (broadcast)frames on bridges. Example:    macvlan0       |      br0     /     ethX    ethY ethX (or Y) receives a L2 multicast or broadcast packet containing an IP packet, flow is not yet in conntrack table. 1. skb passes through bridge and fake-ip (br_netfilter)Prerouting.    -> skb->_nfct now references a unconfirmed entry 2. skb is broad/mcast packet. bridge now passes clones out on each bridge    interface. 3. skb gets passed up the stack. 4. In macvlan case, macvlan driver retains clone(s) of the mcast skb    and schedules a work queue to send them out on the lower devices.    The clone skb->_nfct is not a copy, it is the same entry as the    original skb.  The macvlan rx handler then returns RX_HANDLER_PASS. 5. Normal conntrack hooks (in NF_INET_LOCAL_IN) confirm the orig skb.The Macvlan broadcast worker and normal confirm path will race.This race will not happen if step 2 already confirmed a clone. In thatcase later steps perform skb_clone() with skb->_nfct already confirmed (inhash table).  This works fine.But such confirmation won t happen when eb/ip/nftables rules dropped thepackets before they reached the nf_confirm step in postrouting.Pablo points out that nf_conntrack_bridge doesn t allow use of statefulnat, so we can safely discard the nf_conn entry and let inet callconntrack again.This doesn t work for bridge netfilter: skb could have a nattransformation. Also bridge nf prevents re-invocation of inet preroutingvia  sabotage_in  hook.Work around this problem by explicit confirmation of the entry at LOCAL_INtime, before upper layer has a chance to clone the unconfirmed entry.The downside is that this disables NAT and conntrack helpers.Alternative fix would be to add locking to all code parts that deal withunconfirmed packets, but even if that could be done in a sane way thisopens up other problems, for example:-m physdev --physdev-out eth0 -j SNAT --snat-to 1.2.3.4-m physdev --physdev-out eth1 -j SNAT --snat-to 1.2.3.5For multicast case, only one of such conflicting mappings will becreated, conntrack only handles 1:1 NAT mappings.Users should set create a setup that explicitly marks such trafficNOTRACK (conntrack bypass) to avoid this, but we cannot auto-bypassthem, ruleset might have accept rules for untracked traffic already,so user-visible behaviour would change.
 漏洞公开时间：2024-05-17 20:15
 漏洞创建时间：2024-05-28 01:37:17
 漏洞详情参考链接：
  https://nvd.nist.gov/vuln/detail/CVE-2024-27415
<details>
<summary>更多参考(点击展开)</summary>

| 参考来源 | 参考链接 | 来源链接 |
| ------- | -------- | -------- |
| suse_bugzilla | http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-27415 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-27415.mbox | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/stable/c/7c3f28599652acf431a2211168de4a583f30b6d5 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/stable/c/2b1414d5e94e477edff1d2c79030f1d742625ea0 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/stable/c/80cd0487f630b5382734997c3e5e3003a77db315 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/stable/c/cb734975b0ffa688ff6cc0eed463865bf07b6c01 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://git.kernel.org/stable/c/62e7151ae3eb465e0ab52a20c941ff33bb6332e9 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://www.cve.org/CVERecord?id=CVE-2024-27415 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| suse_bugzilla | https://bugzilla.redhat.com/show_bug.cgi?id=2281101 | https://bugzilla.suse.com/show_bug.cgi?id=1224757 |
| redhat_bugzilla | https://lore.kernel.org/linux-cve-announce/2024051702-CVE-2024-27415-dcae@gregkh/T | https://bugzilla.redhat.com/show_bug.cgi?id=2281101 |
| redhat_bugzilla | https://access.redhat.com/errata/RHSA-2024:5928 | https://bugzilla.redhat.com/show_bug.cgi?id=2281101 |
| debian |  | https://security-tracker.debian.org/tracker/CVE-2024-27415 |

</details>

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：
  <details>
<summary>详情(点击展开)</summary>

无
</details>

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:netfilter: bridge: confirm multicast packets before passing them up the stackconntrack nf_confirm logic cannot handle cloned skbs referencingthe same nf_conn entry, which will happen for multicast (broadcast)frames on bridges. Example:    macvlan0       |      br0     /     ethX    ethY ethX (or Y) receives a L2 multicast or broadcast packet containing an IP packet, flow is not yet in conntrack table. 1. skb passes through bridge and fake-ip (br_netfilter)Prerouting.    -> skb->_nfct now references a unconfirmed entry 2. skb is broad/mcast packet. bridge now passes clones out on each bridge    interface. 3. skb gets passed up the stack. 4. In macvlan case, macvlan driver retains clone(s) of the mcast skb    and schedules a work queue to send them out on the lower devices.    The clone skb->_nfct is not a copy, it is the same entry as the    original skb.  The macvlan rx handler then returns RX_HANDLER_PASS. 5. Normal conntrack hooks (in NF_INET_LOCAL_IN) confirm the orig skb.The Macvlan broadcast worker and normal confirm path will race.This race will not happen if step 2 already confirmed a clone. In thatcase later steps perform skb_clone() with skb->_nfct already confirmed (inhash table).  This works fine.But such confirmation won t happen when eb/ip/nftables rules dropped thepackets before they reached the nf_confirm step in postrouting.Pablo points out that nf_conntrack_bridge doesn t allow use of statefulnat, so we can safely discard the nf_conn entry and let inet callconntrack again.This doesn t work for bridge netfilter: skb could have a nattransformation. Also bridge nf prevents re-invocation of inet preroutingvia  sabotage_in  hook.Work around this problem by explicit confirmation of the entry at LOCAL_INtime, before upper layer has a chance to clone the unconfirmed entry.The downside is that this disables NAT and conntrack helpers.Alternative fix would be to add locking to all code parts that deal withunconfirmed packets, but even if that could be done in a sane way thisopens up other problems, for example:-m physdev --physdev-out eth0 -j SNAT --snat-to 1.2.3.4-m physdev --physdev-out eth1 -j SNAT --snat-to 1.2.3.5For multicast case, only one of such conflicting mappings will becreated, conntrack only handles 1:1 NAT mappings.Users should set create a setup that explicitly marks such trafficNOTRACK (conntrack bypass) to avoid this, but we cannot auto-bypassthem, ruleset might have accept rules for untracked traffic already,so user-visible behaviour would change.
 openEuler评分：
  6.5
 Vector：CVSS：3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
 受影响版本排查(受影响/不受影响)：
  1.openEuler-20.03-LTS-SP4(4.19.90):受影响
2.openEuler-22.03-LTS-SP1(5.10.0):受影响
3.openEuler-22.03-LTS-SP3(5.10.0):受影响
4.openEuler-22.03-LTS-SP4(5.10.0):受影响
5.master(6.6.0):不受影响
6.openEuler-24.03-LTS(6.6.0):不受影响
7.openEuler-24.03-LTS-Next(6.6.0):不受影响

修复是否涉及abi变化(是/否)：
  1.openEuler-20.03-LTS-SP4(4.19.90):否
2.openEuler-22.03-LTS-SP1(5.10.0):否
3.openEuler-22.03-LTS-SP3(5.10.0):否
4.master(6.6.0):否
5.openEuler-24.03-LTS(6.6.0):否
6.openEuler-24.03-LTS-Next(6.6.0):否
7.openEuler-22.03-LTS-SP4(5.10.0):否

原因说明：
  1.master(6.6.0):
2.openEuler-20.03-LTS-SP4(4.19.90):
3.openEuler-22.03-LTS-SP1(5.10.0):
4.openEuler-22.03-LTS-SP3(5.10.0):
5.openEuler-22.03-LTS-SP4(5.10.0):
6.openEuler-24.03-LTS(6.6.0):
7.openEuler-24.03-LTS-Next(6.6.0):

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