Messages in this thread |  | | Date | Mon, 13 Apr 2015 23:48:27 +0800 | From | Adam Lee <> | Subject | Re: [PATCH] cdc-acm: prevent infinite loop when parsing CDC headers. |
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On Mon, Apr 13, 2015 at 05:24:04PM +0200, Quentin Casasnovas wrote: > Phil and I found out a problem with commit: > > 7e860a6e ("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.
Yes, "elength = buffer[0]" should be moved to the front of USB_DT_CS_INTERFACE check, ACK this part.
But I don't know in what case the buffer[0] could be zero, if it happens, better to set elength 1 then goto next_desc? (I'm not a maintainer, pleas also consider others' opinion)
-- Adam Lee http://adam8157.info
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