Restricting path name lookup with openat2()

Posted Aug 23, 2019 22:21 UTC (Fri) by josh (subscriber, #17465)
In reply to: Restricting path name lookup with openat2() by cyphar
Parent article: Restricting path name lookup with openat2()

You don't need to have a separate size field, just reserve one of the flags in the flags field to indicate future structure growth. Then, some future version that needs to add more data to the structure can set that flag.

Restricting path name lookup with openat2()

Posted Aug 24, 2019 5:54 UTC (Sat) by buck (subscriber, #55985) [Link] (1 responses)

forgive me if this is covered on the kernel developers list or is a common antipattern. (if so, please feel free to dismiss this with an informative link in reply). but why not start the structure with a protocol version number, like network packets (e.g., IP first nibble, kerberos protocol messages' and SNMP PDUs' first integer)? then you pass in whatever struct is appropriate to the protocol version, with its size (a la socklen_t of bind(2)), and the kernel checks the protocol version at the top to figure out which structure it's been passed and how to interpret

Restricting path name lookup with openat2()

Posted Aug 24, 2019 20:05 UTC (Sat) by quotemstr (subscriber, #45331) [Link]

The size *is* a protocol version number, essentially.