can: mcba_usb: fix memory leak in mcba_usb

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: can: mcba_usb: fix memory leak in mcba_usb Syzbot reported memory leak in SocketCAN driver for Microchip CAN BUS Analyzer Tool. The problem was in unfreed usb_coherent. In mcba_usb_start() 20 coherent buffers are allocated and there is nothing, that frees them: 1) In callback function the urb is resubmitted and that's all 2) In disconnect function urbs are simply killed, but URB_FREE_BUFFER is not set (see mcba_usb_start) and this flag cannot be used with coherent buffers. Fail log: | [ 1354.053291][ T8413] mcba_usb 1-1:0.0 can0: device disconnected | [ 1367.059384][ T8420] kmemleak: 20 new suspected memory leaks (see /sys/kernel/debug/kmem) So, all allocated buffers should be freed with usb_free_coherent() explicitly NOTE: The same pattern for allocating and freeing coherent buffers is used in drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c

References

• https://git.kernel.org/stable/c/89df95ce32be204eef2e7d4b2f6fb552fb191a68
• https://git.kernel.org/stable/c/a115198caaab6d663bef75823a3c5f0802306d60
• https://git.kernel.org/stable/c/6f87c0e21ad20dd3d22108e33db1c552dfa352a0
• https://git.kernel.org/stable/c/6bd3d80d1f019cefa7011056c54b323f1d8b8e83
• https://git.kernel.org/stable/c/d0760a4ef85697bc756d06eae17ae27f3f055401
• https://git.kernel.org/stable/c/91c02557174be7f72e46ed7311e3bea1939840b0