from http://www.reddit.com/r/netsec/comments/209h4d/samsung_galax... :
This is not a backdoor. It's a feature, and a reasonably common one for Qualcomm based devices.
It's an interface to allow the modem access to a persistent data store (ie. eMMC modem partitions) even though only the application processor may access the MMC controller.
Have a look at the rmt_storage client documentation found in a Qualcomm kernel tree. It used to be pretty common to ship a rmt_storage daemon to do the very same thing Samsung is being accused of here (hint: Nexus 5 still uses it), I don't know about other recent devices, but I'd imagine they'd employ something similar.
Also, there are many more ways for the baseband to compromise the application processor, without an explicit interface.
from http://www.reddit.com/r/netsec/comments/209h4d/samsung_galax... : This is not a backdoor. It's a feature, and a reasonably common one for Qualcomm based devices. It's an interface to allow the modem access to a persistent data store (ie. eMMC modem partitions) even though only the application processor may access the MMC controller. Have a look at the rmt_storage client documentation found in a Qualcomm kernel tree. It used to be pretty common to ship a rmt_storage daemon to do the very same thing Samsung is being accused of here (hint: Nexus 5 still uses it), I don't know about other recent devices, but I'd imagine they'd employ something similar. Also, there are many more ways for the baseband to compromise the application processor, without an explicit interface.