net/sched: cls_api: Don't replay RTM_GETCHAIN in tc_ctl_chain().

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-97958
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:23 UTC
Updated2026-09-25 11:17:23 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: Don't replay RTM_GETCHAIN in tc_ctl_chain(). If a netlink socket sends RTM_GETCHAIN requests repeatedly without recv()ing the responses, tc_ctl_chain() hogs CPU and triggers Hung Task splat. [0] As caught in the stack trace, netlink_attachskb() could confuse tc_ctl_chain() by returning -EAGAIN when the userspace netlink socket's receive buffer is full. The replay: label exists since commit 32a4f5ecd738 ("net: sched: introduce chain object to uapi") but was not used initially. Since commit 9f407f1768d3 ("net: sched: introduce chain templates"), the label is needed for RTM_NEWCHAIN because tcf_proto_lookup_ops() may release RTNL to call request_module(). However, the replay logic is unnecessary for RTM_GETCHAIN. Let's apply the replay logic only for RTM_NEWCHAIN. [0]: INFO: task repro:1018 is blocked on a mutex likely owned by task repro:1022. task:repro state:R running task stack:14096 pid:1022 tgid:1014 ppid:961 task_flags:0x400040 flags:0x00080000 Call Trace: <TASK> ? clockevents_program_event (kernel/time/clockevents.c:372) ? pskb_expand_head (net/core/skbuff.c:615) ? skb_release_data (net/core/skbuff.c:1122) ? netlink_attachskb (./include/linux/skbuff.h:1323 ./include/linux/skbuff.h:1332 net/netlink/af_netlink.c:1232) ? __netlink_lookup (./include/linux/rcupdate.h:882 ./include/linux/rhashtable.h:711 net/netlink/af_netlink.c:499) ? tc_chain_notify (net/sched/cls_api.c:3045) ? tc_chain_notify (./include/linux/skbuff.h:1384 net/sched/cls_api.c:3041) ? netlink_unicast (net/netlink/af_netlink.c:1335) ? rtnl_unicast (./include/net/netlink.h:1198 net/core/rtnetlink.c:985) ? tc_ctl_chain (net/sched/cls_api.c:3242) ? rtnetlink_rcv_msg (net/core/rtnetlink.c:7146) ? netlink_unicast (net/netlink/af_netlink.c:1354) ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:7177) ? netlink_rcv_skb (net/netlink/af_netlink.c:2556) ? netlink_unicast (net/netlink/af_netlink.c:1319) ? netlink_sendmsg (net/netlink/af_netlink.c:1900) ? __sock_sendmsg (net/socket.c:800) ? __sys_sendto (net/socket.c:2281) ? __x64_sys_sendto (net/socket.c:2288 net/socket.c:2284 net/socket.c:2284) ? do_syscall_64 (arch/x86/entry/syscall_64.c:61 arch/x86/entry/syscall_64.c:84) ? entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK>

Risk And Classification

EPSS: 0.001680000 probability, percentile 0.054070000 (date 2026-09-27)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2ed9db3074fcd8d12709fe40ff0e691d74229818 a1c2840d95af1fa3d83ba71e23fa0c674a4c6796 git Not specified
CNA Linux Linux affected 2ed9db3074fcd8d12709fe40ff0e691d74229818 503ba58481e3ba69d28127d35a39cec529f9670c git Not specified
CNA Linux Linux affected 2ed9db3074fcd8d12709fe40ff0e691d74229818 e9ac395bb56122a057d0aa91a6b55d9e3fa37c26 git Not specified
CNA Linux Linux affected 2ed9db3074fcd8d12709fe40ff0e691d74229818 dff39930ad5e53d202bfdfb14687d1d2fd753b4d git Not specified
CNA Linux Linux affected 4.19 Not specified
CNA Linux Linux unaffected 4.19 semver Not specified
CNA Linux Linux unaffected 6.12.111 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.53 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/503ba58481e3ba69d28127d35a39cec529f9670c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a1c2840d95af1fa3d83ba71e23fa0c674a4c6796 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e9ac395bb56122a057d0aa91a6b55d9e3fa37c26 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dff39930ad5e53d202bfdfb14687d1d2fd753b4d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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