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CVE-2024-26804— net: ip_tunnel: prevent perpetual headroom growth

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 net ip_tunnel中存在安全问题。

CVSS 7.8 · High EPSS 0.25% · P15

Possible ATT&CK Techniques 1 AI

T1498.001 · Direct Network Flood

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 243aad830e8a4cdda261626fbaeddde16b08d04a< f81e94d2dcd2397137edcb8b85f4c5bed5d22383 affected
243aad830e8a4cdda261626fbaeddde16b08d04a< 2e95350fe9db9d53c701075060ac8ac883b68aee affected
243aad830e8a4cdda261626fbaeddde16b08d04a< afec0c5cd2ed71ca95a8b36a5e6d03333bf34282 affected
243aad830e8a4cdda261626fbaeddde16b08d04a< ab63de24ebea36fe73ac7121738595d704b66d96 affected
243aad830e8a4cdda261626fbaeddde16b08d04a< a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9 affected
243aad830e8a4cdda261626fbaeddde16b08d04a< 049d7989c67e8dd50f07a2096dbafdb41331fb9b affected
243aad830e8a4cdda261626fbaeddde16b08d04a< 5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f affected
03017375b0122453e6dda833ff7bd4191915def5 affected
… +10 more rows
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I. Basic Information for CVE-2024-26804

Vulnerability Information
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Vulnerability Title
net: ip_tunnel: prevent perpetual headroom growth
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: ip_tunnel: prevent perpetual headroom growth syzkaller triggered following kasan splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 Read 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 is more than 64k and skb->network_header (u16) has wrapped around. The bug is in the ip_tunnel infrastructure, which can cause dev->needed_headroom to increment ad infinitum. The syzkaller reproducer consists of packets getting routed via a gre tunnel, 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 future output device, rt.dev->needed_headroom (ipip0). 3). ip output / start_xmit moves skb on to ipip0. which runs the same code path again (xmit recursion). 4). Routing step for the post-gre0-encap packet finds gre0 as output device to 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 step incremented rt->dev (gre0) headroom, and ipip0 incremented because gre0 needed_headroom was increased. For each subsequent packet, gre/ipip0->needed_headroom grows until post-expand-head reallocations result in a skb->head/data distance of more than 64k. Once that happens, skb->network_header (u16) wraps around when pskb_expand_head tries to make sure that skb_network_offset() is unchanged after 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 the network header) makes skb->data point to a memory location outside skb->head area. v2: Cap the needed_headroom update to an arbitarily chosen upperlimit to prevent perpetual increase instead of dropping the headroom increment completely.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 net ip_tunnel中存在安全问题。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 243aad830e8a4cdda261626fbaeddde16b08d04a ~ f81e94d2dcd2397137edcb8b85f4c5bed5d22383 -
Linux Linux 2.6.34 -

II. Public POCs for CVE-2024-26804

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III. Intelligence Information for CVE-2024-26804

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Mailing List Discussions for CVE-2024-26804 (1)

Other References for CVE-2024-26804 (7)

Same Patch Batch · Linux · 2024-04-04 · 32 CVEs total

CVE-2024-26782 9.8 CRITICAL mptcp: fix double-free on socket dismantle
CVE-2024-26800 9.8 CRITICAL tls: fix use-after-free on failed backlog decryption
CVE-2024-26801 8.8 HIGH Bluetooth: Avoid potential use-after-free in hci_error_reset
CVE-2024-26792 7.8 HIGH btrfs: fix double free of anonymous device after snapshot creation failure
CVE-2024-26809 7.8 HIGH netfilter: nft_set_pipapo: release elements in clone only from destroy path
CVE-2024-26808 7.8 HIGH netfilter: nft_chain_filter: handle NETDEV_UNREGISTER for inet/ingress basechain
CVE-2024-26807 7.8 HIGH spi: cadence-qspi: fix pointer reference in runtime PM hooks
CVE-2024-26802 7.8 HIGH stmmac: Clear variable when destroying workqueue
CVE-2024-26797 7.8 HIGH drm/amd/display: Prevent potential buffer overflow in map_hw_resources
CVE-2024-26795 7.8 HIGH riscv: Sparse-Memory/vmemmap out-of-bounds fix
CVE-2024-26793 7.8 HIGH gtp: fix use-after-free and null-ptr-deref in gtp_newlink()
CVE-2024-26789 7.8 HIGH crypto: arm64/neonbs - fix out-of-bounds access on short input
CVE-2024-26786 7.8 HIGH iommufd: Fix iopt_access_list_id overwrite bug
CVE-2024-26799 7.0 HIGH ASoC: qcom: Fix uninitialized pointer dmactl
CVE-2024-26746 dmaengine: idxd: Ensure safe user copy of completion record
CVE-2024-26788 dmaengine: fsl-qdma: init irq after reg initialization
CVE-2024-26750 af_unix: Drop oob_skb ref before purging queue in GC.
CVE-2024-26780 af_unix: Fix task hung while purging oob_skb in GC.
CVE-2024-26806 spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks
CVE-2024-26805 netlink: Fix kernel-infoleak-after-free in __skb_datagram_iter

Showing top 20 of 32 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2024-26804

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