Formal sound verification of Linuxs USB BP keyboard driver Willem - PowerPoint PPT Presentation

Formal sound verification of Linux’s USB BP keyboard driver Willem Penninckx Jan Tobias Mühlberg Jan Smans Bart Jacobs Frank Piessens

Table Of Contents ● What did we do? ● How did we do it? ● What did we learn?

Table Of Contents ● What did we do? ● How did we do it? ● What did we learn?

Formal sound verification Check properties: Bug hunting ● Never crashes ● No race-condition If “green bar”, then ● API rules verified property always holds ● Real-world software toy ● Unbounded number of threads ● Unbounded number of keyboards Linux’s USB BP keyboard driver

Table Of Contents ● What did we do? ● How did we do it? ● What did we learn?

usbkbd.c input.h /*@ /*@ Formal * preCond * PreCond * postCond API * PostCond @*/ specs @*/ void input_register(); void fun1() { c_code; usb.h //@ ghostcode c_code; /*@ usb_core.c c_code; * preCond } * postCond void @*/ usb_kill_urb() { void usb_kill_urb(); c_code; c_code; /*@ c_code; * (ghost code) } @*/

usbkbd.c /*@ * PreCond * PostCond @*/ void fun1() { c_code; //@ ghostcode c_code; c_code; } Tool: VeriFast

Table Of Contents ● What did we do? ● How did we do it? ● What did we learn?

Learned / Conclusions Possible to combine: ● Soundness ● Unbounded #threads ● Real driver ● API usage rules File Lines C Lines annot Tool speed usbkbd.c 329 822 ~1 second API headers / 769 Bugs found ● Unloading bug ● Synchronization bug Patches are in Linux 3.3 http://people.cs.kuleuven.be/~willem.penninckx/usbkbd/

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