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CVE-2021-47482

Disclosure Date: May 22, 2024 •
CVE-2021-47482
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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_meshfree() 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.

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CVSS V3 Severity and Metrics
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General Information

Offensive Application
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Utility Class
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Ports
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OS
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Vulnerable Versions
Linux 0c6b199f09be
Linux not down converted
Prerequisites
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Metasploit Module
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Vendors

  • Linux

Products

  • Linux
Technical Analysis