# CVE-2021-47482: net: batman-adv: fix error handling

- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-22 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.38

## Description

In the Linux kernel, the following vulnerability has been resolved: net: batman-adv: fix error handling Syzbot reported ODEBUG warning in batadv_nc_mesh_free(). The problem was in wrong error handling in batadv_mesh_init(). Before this patch batadv_mesh_init() was calling batadv_mesh_free() in case of any batadv_*_init() calls failure. This approach may work well, when there is some kind of indicator, which can tell which parts of batadv are initialized; but there isn't any. All written above lead to cleaning up uninitialized fields. Even if we hide ODEBUG warning by initializing bat_priv->nc.work, syzbot was able to hit GPF in batadv_nc_purge_paths(), because hash pointer in still NULL. [1] To fix these bugs we can unwind batadv_*_init() calls one by one. It is good approach for 2 reasons: 1) It fixes bugs on error handling path 2) It improves the performance, since we won't call unneeded batadv_*_free() functions. So, this patch makes all batadv_*_init() clean up all allocated memory before returning with an error to no call correspoing batadv_*_free() and open-codes batadv_mesh_free() with proper order to avoid touching uninitialized fields.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
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## 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/0c6b199f09be489c48622537a550787fc80aea73
- https://git.kernel.org/stable/c/07533f1a673ce1126d0a72ef1e4b5eaaa3dd6d20
- https://git.kernel.org/stable/c/e50f957652190b5a88a8ebce7e5ab14ebd0d3f00
- https://git.kernel.org/stable/c/fbf150b16a3635634b7dfb7f229d8fcd643c6c51
- https://git.kernel.org/stable/c/6422e8471890273994fe8cc6d452b0dcd2c9483e
- https://git.kernel.org/stable/c/b0a2cd38553c77928ef1646ed1518486b1e70ae8
- https://git.kernel.org/stable/c/a8f7359259dd5923adc6129284fdad12fc5db347
- https://git.kernel.org/stable/c/6f68cd634856f8ca93bafd623ba5357e0f648c68

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