概要

In the Linux kernel, the following vulnerability has been resolved:batman-adv: Avoid infinite loop trying to resize local TTIf the MTU of one of an attached interface becomes too small to transmitthe local translation table then it must be resized to fit inside allfragments (when enabled) or a single packet.But if the MTU becomes too low to transmit even the header + the VLANspecific part then the resizing of the local TT will never succeed. Thiscan for example happen when the usable space is 110 bytes and 11 VLANs areon top of batman-adv. In this case, at least 116 byte would be needed.There will just be an endless spam of batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (110)in the log but the function will never finish. Problem here is that thetimeout will be halved all the time and will then stagnate at 0 andtherefore never be able to reduce the table even more.There are other scenarios possible with a similar result. The number ofBATADV_TT_CLIENT_NOPURGE entries in the local TT can for example be toohigh to fit inside a packet. Such a scenario can therefore happen also withonly a single VLAN + 7 non-purgable addresses - requiring at least 120bytes.While this should be handled proactively when:* interface with too low MTU is added* VLAN is added* non-purgeable local mac is added* MTU of an attached interface is reduced* fragmentation setting gets disabled (which most likely requires dropping attached interfaces)not all of these scenarios can be prevented because batman-adv is onlyconsuming events without the the possibility to prevent these actions(non-purgable MAC address added, MTU of an attached interface is reduced).It is therefore necessary to also make sure that the code is able to handlealso the situations when there were already incompatible systemconfiguration are present.

CVSS v3 指标

安全公告

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