AZL-43306

In the Linux kernel, the following vulnerability has been resolved:

net: batman-adv: fix error handling

Syzbot reported ODEBUG warning in batadvncmeshfree(). The problem was in wrong error handling in batadvmesh_init().

Before this patch batadvmeshinit() was calling batadvmeshfree() 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 batpriv->nc.work, syzbot was able to hit GPF in batadvncpurgepaths(), 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 batadvmesh_free() with proper order to avoid touching uninitialized fields.