Comment 0 for bug 1460657

Bug #1413992 's patch introduced a possible infinite loop.

commit 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e
Author: Quentin Casasnovas <email address hidden>
Date: Tue Apr 14 11:25:43 2015 +0200

    cdc-acm: prevent infinite loop when parsing CDC headers.

    Phil and I found out a problem with commit:

      7e860a6e7aa6 ("cdc-acm: add sanity checks")

    It added some sanity checks to ignore potential garbage in CDC headers but
    also introduced a potential infinite loop. This can happen at the first
    loop iteration (elength = 0 in that case) if the description isn't a
    DT_CS_INTERFACE or later if 'buffer[0]' is zero.

    It should also be noted that the wrong length was being added to 'buffer'
    in case 'buffer[1]' was not a DT_CS_INTERFACE descriptor, since elength was
    assigned after that check in the loop.

    A specially crafted USB device could be used to trigger this infinite loop.

    Fixes: 7e860a6e7aa6 ("cdc-acm: add sanity checks")
    Signed-off-by: Phil Turnbull <email address hidden>
    Signed-off-by: Quentin Casasnovas <email address hidden>
    CC: Sergei Shtylyov <email address hidden>
    CC: Oliver Neukum <email address hidden>
    CC: Adam Lee <email address hidden>
    CC: <email address hidden>
    Signed-off-by: Greg Kroah-Hartman <email address hidden>