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bpf: Fix register equivalence tracking. #239

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wants to merge 2 commits into from
Closed

bpf: Fix register equivalence tracking. #239

wants to merge 2 commits into from

Commits on Oct 14, 2020

  1. adding ci files

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    kernel-patches-bot committed Oct 14, 2020
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  2. bpf: Fix register equivalence tracking. 

    The 64-bit JEQ/JNE handling in reg_set_min_max() was clearing reg->id in either
true or false branch. In the case 'if (reg->id)' check was done on the other
branch the counter part register would have reg->id == 0 when called into
find_equal_scalars(). In such case the helper would incorrectly identify other
registers with id == 0 as equivalent and propagate the state incorrectly.
Fix it by preserving ID across reg_set_min_max().
In other words any kind of comparison operator on the scalar register
should preserve its ID to recognize:
r1 = r2
if (r1 == 20) {
  #1 here both r1 and r2 == 20
} else if (r2 < 20) {
  #2 here both r1 and r2 < 20
}

The patch is addressing #1 case. The #2 was working correctly already.

Fixes: 7574883 ("bpf: Propagate scalar ranges through register assignments.")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    @kernel-patches-bot
    Alexei Starovoitov authored and kernel-patches-bot committed Oct 14, 2020
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