一、漏洞信息
漏洞编号：CVE-2024-26804
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:net: ip_tunnel: prevent perpetual headroom growthsyzkaller triggered following kasan splat:BUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170Read of size 1 at addr ffff88812fb4000e by task syz-executor183/5191[..] kasan_report+0xda/0x110 mm/kasan/report.c:588 __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline] ___skb_get_hash net/core/flow_dissector.c:1791 [inline] __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856 skb_get_hash include/linux/skbuff.h:1556 [inline] ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308 __netdev_start_xmit include/linux/netdevice.h:4940 [inline] netdev_start_xmit include/linux/netdevice.h:4954 [inline] xmit_one net/core/dev.c:3548 [inline] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349 dev_queue_xmit include/linux/netdevice.h:3134 [inline] neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592 ... ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235 ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323 .. iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831 ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665 __netdev_start_xmit include/linux/netdevice.h:4940 [inline] netdev_start_xmit include/linux/netdevice.h:4954 [inline] xmit_one net/core/dev.c:3548 [inline] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 ...The splat occurs because skb->data points past skb->head allocated area.This is because neigh layer does: __skb_pull(skb, skb_network_offset(skb));... but skb_network_offset() returns a negative offset and __skb_pull()arg is unsigned. IOW, we skb->data gets adjusted by a huge value.The negative value is returned because skb->head and skb->data distance ismore than 64k and skb->network_header (u16) has wrapped around.The bug is in the ip_tunnel infrastructure, which can causedev->needed_headroom to increment ad infinitum.The syzkaller reproducer consists of packets getting routed via a gretunnel, and route of gre encapsulated packets pointing at another (ipip)tunnel. The ipip encapsulation finds gre0 as next output device.This results in the following pattern:1). First packet is to be sent out via gre0.Route lookup found an output device, ipip0.2).ip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the futureoutput device, rt.dev->needed_headroom (ipip0).3).ip output / start_xmit moves skb on to ipip0. which runs the samecode path again (xmit recursion).4).Routing step for the post-gre0-encap packet finds gre0 as output deviceto use for ipip0 encapsulated packet.tunl0->needed_headroom is then incremented based on the (already bumped)gre0 device headroom.This repeats for every future packet:gre0->needed_headroom gets inflated because previous packets ipip0 stepincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0needed_headroom was increased.For each subsequent packet, gre/ipip0->needed_headroom grows untilpost-expand-head reallocations result in a skb->head/data distance ofmore than 64k.Once that happens, skb->network_header (u16) wraps around whenpskb_expand_head tries to make sure that skb_network_offset() is unchangedafter the headroom expansion/reallocation.After this skb_network_offset(skb) returns a different (and negative)result post headroom expansion.The next trip to neigh layer (or anything else that would __skb_pull thenetwork header) makes skb->data point to a memory location outsideskb->head area.v2: Cap the needed_headroom update to an arbitarily chosen upperlimit toprevent perpetual increase instead of dropping the headroom incrementcompletely.
漏洞公开时间：2024-04-04 17:15:09
漏洞创建时间：2024-04-04 18:17:24
漏洞详情参考链接：
https://nvd.nist.gov/vuln/detail/CVE-2024-26804

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:net: ip_tunnel: prevent perpetual headroom growthsyzkaller triggered following kasan splat:BUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170Read of size 1 at addr ffff88812fb4000e by task syz-executor183/5191[..] kasan_report+0xda/0x110 mm/kasan/report.c:588 __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline] ___skb_get_hash net/core/flow_dissector.c:1791 [inline] __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856 skb_get_hash include/linux/skbuff.h:1556 [inline] ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308 __netdev_start_xmit include/linux/netdevice.h:4940 [inline] netdev_start_xmit include/linux/netdevice.h:4954 [inline] xmit_one net/core/dev.c:3548 [inline] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349 dev_queue_xmit include/linux/netdevice.h:3134 [inline] neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592 ... ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235 ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323 .. iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831 ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665 __netdev_start_xmit include/linux/netdevice.h:4940 [inline] netdev_start_xmit include/linux/netdevice.h:4954 [inline] xmit_one net/core/dev.c:3548 [inline] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 ...The splat occurs because skb->data points past skb->head allocated area.This is because neigh layer does: __skb_pull(skb, skb_network_offset(skb));... but skb_network_offset() returns a negative offset and __skb_pull()arg is unsigned. IOW, we skb->data gets adjusted by a huge value.The negative value is returned because skb->head and skb->data distance ismore than 64k and skb->network_header (u16) has wrapped around.The bug is in the ip_tunnel infrastructure, which can causedev->needed_headroom to increment ad infinitum.The syzkaller reproducer consists of packets getting routed via a gretunnel, and route of gre encapsulated packets pointing at another (ipip)tunnel. The ipip encapsulation finds gre0 as next output device.This results in the following pattern:1). First packet is to be sent out via gre0.Route lookup found an output device, ipip0.2).ip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the futureoutput device, rt.dev->needed_headroom (ipip0).3).ip output / start_xmit moves skb on to ipip0. which runs the samecode path again (xmit recursion).4).Routing step for the post-gre0-encap packet finds gre0 as output deviceto use for ipip0 encapsulated packet.tunl0->needed_headroom is then incremented based on the (already bumped)gre0 device headroom.This repeats for every future packet:gre0->needed_headroom gets inflated because previous packets ipip0 stepincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0needed_headroom was increased.For each subsequent packet, gre/ipip0->needed_headroom grows untilpost-expand-head reallocations result in a skb->head/data distance ofmore than 64k.Once that happens, skb->network_header (u16) wraps around whenpskb_expand_head tries to make sure that skb_network_offset() is unchangedafter the headroom expansion/reallocation.After this skb_network_offset(skb) returns a different (and negative)result post headroom expansion.The next trip to neigh layer (or anything else that would __skb_pull thenetwork header) makes skb->data point to a memory location outsideskb->head area.v2: Cap the needed_headroom update to an arbitarily chosen upperlimit toprevent perpetual increase instead of dropping the headroom incrementcompletely.
openEuler评分：
5.5
Vector：CVSS：2.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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