On Fri, Mar 01, 2019 at 10:05:29PM +0100, Daniel Borkmann wrote:
> Marek reported that he saw an issue with the below snippet in that
> timing measurements where off when loaded as unpriv while results
> were reasonable when loaded as privileged:
>
> [...]
> uint64_t a = bpf_ktime_get_ns();
> uint64_t b = bpf_ktime_get_ns();
> uint64_t delta = b - a;
> if ((int64_t)delta > 0) {
> [...]
>
> Turns out there is a bug where a corner case is missing in the fix
> d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar
> type from different paths"), namely fixup_bpf_calls() only checks
> whether aux has a non-zero alu_state, but it also needs to test for
> the case of BPF_ALU_NON_POINTER since in both occasions we need to
> skip the masking rewrite (as there is nothing to mask).
>
> Fixes: d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar
> type from different paths")
> Reported-by: Marek Majkowski <[email protected]>
> Reported-by: Arthur Fabre <[email protected]>
> Signed-off-by: Daniel Borkmann <[email protected]>
> Link:
> https://lore.kernel.org/netdev/cajpywtjqp34ck20ilm5ymumz9kxqodu1-+bzrgmagglubwz...@mail.gmail.com/T/
Applied, Thanks
