CVE-2021-47482 net: batman-adv: fix error handling
A null pointer dereference in the Linux kernel's batman-adv module can cause a system crash during error handling.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-47482?
CVE-2021-47482 is a medium-severity vulnerability in Linux kernel, published on 22 May 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-544
Which versions are affected by CVE-2021-47482?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-47482?
Apply the vendor's patch.
Is CVE-2021-47482 being exploited?
There is no known exploitation of CVE-2021-47482 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-43306, DEBIAN-CVE-2021-47482, GHSA-xgm7-3x53-gq2c, UBUNTU-CVE-2021-47482.