CVE-2026-97958

Status: UPDATED  |  Advisory ID: CVE-2026-97958

Key Details

Affected Products, Subsystems & Sectors

What to Know

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> (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References