Messages in this thread | | | Date | Fri, 4 Dec 2015 12:35:23 -0800 | From | Alexei Starovoitov <> | Subject | Re: bpf: undefined shift in __bpf_prog_run |
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On Fri, Dec 04, 2015 at 08:48:57PM +0100, Dmitry Vyukov wrote: > > For example, a compiler can assume that result of left shift is larger > or equal to first operand, which in turn can allow it to elide some > bounds check in code, which in turn can lead to an exploit. I am not > saying that this particular pattern is present in the code, what I > want to say is that such undefined behaviors can lead to very > unpredictable and unexpected consequences.
Within bpf it cannot. shift is not used in any memory or bounds operations. so reg <<= 1234 cannot be exploited.
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