Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:s390/ism: fix concurrency management in ism_cmd()The s390x ISM device data sheet clearly states that only onerequest-response sequence is allowable per ISM function at any point intime. Unfortunately as of today the s390/ism driver in Linux does nothonor that requirement. This patch aims to rectify that.This problem was discovered based on Aliaksei's bug report which statesthat for certain workloads the ISM functions end up entering error state(with PEC 2 as seen from the logs) after a while and as a consequenceconnections handled by the respective function break, and for futureconnection requests the ISM device is not considered -- given it is in adysfunctional state. During further debugging PEC 3A was observed aswell.A kernel message like[ 1211.244319] zpci: 061a:00:00.0: Event 0x2 reports an error for PCI function 0x61ais a reliable indicator of the stated function entering error statewith PEC 2. Let me also point out that a kernel message like[ 1211.244325] zpci: 061a:00:00.0: The ism driver bound to the device does not support error recoveryis a reliable indicator that the ISM function won't be auto-recoveredbecause the ISM driver currently lacks support for it.On a technical level, without this synchronization, commands (inputs tothe FW) may be partially or fully overwritten (corrupted) by another CPUtrying to issue commands on the same function. There is hard evidence thatthis can lead to DMB token values being used as DMB IOVAs, leading toPEC 2 PCI events indicating invalid DMA. But this is only one of thefailure modes imaginable. In theory even completely losing one commandand executing another one twice and then trying to interpret the outputsas if the command we intended to execute was actually executed and notthe other one is also possible. Frankly, I don't feel confident aboutproviding an exhaustive list of possible consequences.
No PoCs from references.
- https://github.com/fkie-cad/nvd-json-data-feeds