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

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-22 · updated 2026-06-17
Weakness: CWE-544

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.

Affected products

Linux kernel: from 2.6.38 before 4.4.293; from 4.5 before 4.9.289; from 4.10 before 4.14.254; from 4.15 before 4.19.215; from 4.20 before 5.4.157; from 5.5 before 5.10.77 — fixed in 4.14.254, 4.19.215, 4.4.293, 4.9.289, 5.10.77, 5.14.16

How to fix

Upgrade to a fixed version: Linux kernel 4.14.254, 4.19.215, 4.4.293, 4.9.289. Check the vendor advisory for mitigations.

References

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