net: drop bad gso csum_start and offset in virtio_net_hdr

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-43897
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-08-26 11:15:04 UTC
Updated2026-08-04 11:19:59 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net: drop bad gso csum_start and offset in virtio_net_hdr Tighten csum_start and csum_offset checks in virtio_net_hdr_to_skb for GSO packets. The function already checks that a checksum requested with VIRTIO_NET_HDR_F_NEEDS_CSUM is in skb linear. But for GSO packets this might not hold for segs after segmentation. Syzkaller demonstrated to reach this warning in skb_checksum_help offset = skb_checksum_start_offset(skb); ret = -EINVAL; if (WARN_ON_ONCE(offset >= skb_headlen(skb))) By injecting a TSO packet: WARNING: CPU: 1 PID: 3539 at net/core/dev.c:3284 skb_checksum_help+0x3d0/0x5b0 ip_do_fragment+0x209/0x1b20 net/ipv4/ip_output.c:774 ip_finish_output_gso net/ipv4/ip_output.c:279 [inline] __ip_finish_output+0x2bd/0x4b0 net/ipv4/ip_output.c:301 iptunnel_xmit+0x50c/0x930 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x2296/0x2c70 net/ipv4/ip_tunnel.c:813 __gre_xmit net/ipv4/ip_gre.c:469 [inline] ipgre_xmit+0x759/0xa60 net/ipv4/ip_gre.c:661 __netdev_start_xmit include/linux/netdevice.h:4850 [inline] netdev_start_xmit include/linux/netdevice.h:4864 [inline] xmit_one net/core/dev.c:3595 [inline] dev_hard_start_xmit+0x261/0x8c0 net/core/dev.c:3611 __dev_queue_xmit+0x1b97/0x3c90 net/core/dev.c:4261 packet_snd net/packet/af_packet.c:3073 [inline] The geometry of the bad input packet at tcp_gso_segment: [ 52.003050][ T8403] skb len=12202 headroom=244 headlen=12093 tailroom=0 [ 52.003050][ T8403] mac=(168,24) mac_len=24 net=(192,52) trans=244 [ 52.003050][ T8403] shinfo(txflags=0 nr_frags=1 gso(size=1552 type=3 segs=0)) [ 52.003050][ T8403] csum(0x60000c7 start=199 offset=1536 ip_summed=3 complete_sw=0 valid=0 level=0) Mitigate with stricter input validation. csum_offset: for GSO packets, deduce the correct value from gso_type. This is already done for USO. Extend it to TSO. Let UFO be: udp[46]_ufo_fragment ignores these fields and always computes the checksum in software. csum_start: finding the real offset requires parsing to the transport header. Do not add a parser, use existing segmentation parsing. Thanks to SKB_GSO_DODGY, that also catches bad packets that are hw offloaded. Again test both TSO and USO. Do not test UFO for the above reason, and do not test UDP tunnel offload. GSO packet are almost always CHECKSUM_PARTIAL. USO packets may be CHECKSUM_NONE since commit 10154dbded6d6 ("udp: Allow GSO transmit from devices with no checksum offload"), but then still these fields are initialized correctly in udp4_hwcsum/udp6_hwcsum_outgoing. So no need to test for ip_summed == CHECKSUM_PARTIAL first. This revises an existing fix mentioned in the Fixes tag, which broke small packets with GSO offload, as detected by kselftests.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: NVD-CWE-noinfo

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 27874ca77bd2b05a3779c7b3a5c75d8dd7f0b40f 413e785a89f8bde0d4156a54b8ac2fa003c06756 git Not specified
CNA Linux Linux affected 5b1997487a3f3373b0f580c8a20b56c1b64b0775 f01c5e335fbb7fb612d40f14a3c02e2612a43d3b git Not specified
CNA Linux Linux affected 90d41ebe0cd4635f6410471efc1dd71b33e894cf 6772c4868a8e7ad5305957cdb834ce881793acb7 git Not specified
CNA Linux Linux affected e9164903b8b303c34723177b02fe91e49e3c4cd7 2edbb3e8838c672cd7e247e47989df9d03fc6668 git Not specified
CNA Linux Linux affected e269d79c7d35aa3808b1f3c1737d63dab504ddc8 89add40066f9ed9abe5f7f886fe5789ff7e0c50e git Not specified
CNA Linux Linux affected 5.15.165 5.15.167 semver Not specified
CNA Linux Linux affected 6.1.103 6.1.107 semver Not specified
CNA Linux Linux affected 6.6.44 6.6.46 semver Not specified
CNA Linux Linux affected 6.10.3 6.10.5 semver Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/89add40066f9ed9abe5f7f886fe5789ff7e0c50e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/f01c5e335fbb7fb612d40f14a3c02e2612a43d3b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2edbb3e8838c672cd7e247e47989df9d03fc6668 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/413e785a89f8bde0d4156a54b8ac2fa003c06756 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
lists.debian.org/debian-lts-announce/2025/01/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/6772c4868a8e7ad5305957cdb834ce881793acb7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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