CVE-2026-98300: tcp: Don't call skb_clone_and_charge_r() for close()d listener in tcp_v6_do_rcv().
In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call skbcloneandcharger() for close()d listener in tcpv6dorcv().
tcpv6dorcv() no longer calls skbcloneandcharger() for TCPLISTEN since commit 073d89808c06 ("net: fix data-races around sk->skforwardalloc").
However, there is still a small race window between tcpv6rcv() and tcpv6dorcv(), where concurrent close() changes TCPLISTEN to TCPCLOSE, causing skbcloneandcharger() to be called locklessly and resulting in the splat below. [0]
Let's avoid calling skbcloneandcharger() for TCPCLOSE as well.
This is fine for non-listeners because tcprcvstateprocess() drops skb for TCPCLOSE and optskb was freed immediately anyway.
[0]: sk->skforwardalloc WARNING: net/ipv4/afinet.c:162 at inetsockdestruct+0x64d/0x810 net/ipv4/afinet.c:162, CPU#1: ksoftirqd/1/28 Modules linked in: CPU: 1 UID: 0 PID: 28 Comm: ksoftirqd/1 Not tainted 7.2.0 #17 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 RIP: 0010:inetsockdestruct+0x64d/0x810 net/ipv4/afinet.c:162 Code: 3d 49 ff e9 06 fd ff ff e8 d0 5b 83 f8 90 0f 0b 90 e9 35 fe ff ff e8 c2 5b 83 f8 90 0f 0b 90 e9 c5 fe ff ff e8 b4 5b 83 f8 90 <0f> 0b 90 e9 04 ff ff ff e8 a6 5b 83 f8 90 0f 0b 90 e9 65 fe ff ff RSP: 0018:ffffc90000677bb8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8880117bde80 RCX: ffffffff8957eb41 RDX: ffff88801dad5d00 RSI: ffffffff8957ec3c RDI: 0000000000000005 RBP: 00000000fffff000 R08: ffffffff8957eb41 R09: 00000000fffff000 R10: 0000000000000005 R11: 0000000000000000 R12: dffffc0000000000 R13: ffff8880117bdf10 R14: ffffffff81c08eb7 R15: 0000000000000003 FS: 0000000000000000(0000) GS:ffff8880d7ae5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f93a1021138 CR3: 00000000207a9000 CR4: 0000000000350ef0 Call Trace: <TASK> skdestruct+0x82/0xae0 net/core/sock.c:2356 rcudobatch kernel/rcu/tree.c:2645 [inline] rcucore+0x59c/0x1100 kernel/rcu/tree.c:2897 handlesoftirqs+0x1e4/0x9b0 kernel/softirq.c:622 runksoftirqd kernel/softirq.c:1076 [inline] runksoftirqd+0x38/0x60 kernel/softirq.c:1068 smpbootthreadfn+0x458/0xc80 kernel/smpboot.c:160 kthread+0x396/0x4a0 kernel/kthread.c:436 retfromfork+0x8e0/0xe40 arch/x86/kernel/process.c:158 retfromforkasm+0x1a/0x30 arch/x86/entry/entry64.S:245 </TASK>
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Fixed in 6.6.158.1-1 - Upgrade
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Event History
Frequently Asked Questions
What conditions are required to trigger the race?
The issue requires a TCPv6 receive path to overlap with a concurrent close() that changes a socket from TCP_LISTEN to TCP_CLOSE. In that window, tcp_v6_do_rcv() can call skb_clone_and_charge_r() locklessly.
Which systems are most relevant to triage?
Systems running the Linux kernel with TCPv6 listeners are relevant, particularly where listeners can be closed while IPv6 TCP traffic is being received. The described race concerns the transition from a listening socket to a closed socket.
How can administrators recognize a possible occurrence?
The reported symptom is a kernel WARNING involving sk->sk_forward_alloc in inet_sock_destruct at net/ipv4/af_inet.c:162. The example warning was emitted by ksoftirqd during socket destruction.
What does the resolved change do?
The change prevents tcp_v6_do_rcv() from calling skb_clone_and_charge_r() when the socket is in TCP_CLOSE as well as TCP_LISTEN. For non-listener sockets in TCP_CLOSE, tcp_rcv_state_process() drops the skb and the optional skb was already freed immediately.