In 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>
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>
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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> | |
| Title | net/sched: cls_api: Don't replay RTM_GETCHAIN in tc_ctl_chain(). | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:23:03.753Z
Reserved: 2026-09-25T10:18:58.205Z
Link: CVE-2026-97958
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:23.477
Modified: 2026-09-25T11:17:23.477
Link: CVE-2026-97958
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.