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internal/fuzz: limit the number of consecutive mutations applied to an input #49601

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rolandshoemaker opened this issue Nov 16, 2021 · 3 comments
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internal/fuzz: limit the number of consecutive mutations applied to an input #49601

rolandshoemaker opened this issue Nov 16, 2021 · 3 comments
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FrozenDueToAge fuzz Issues related to native fuzzing support NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.18

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@rolandshoemaker
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Currently, each time an input is sent to the worker a very large number of mutations can be consecutively applied. Resulting in a significantly different input at the end of the fuzzing than at the start. This significantly reduces the diversity of inputs, since a new "interesting" input is likely to be very different from the original input.

Instead we should limit the number of mutations to some small number, resetting the input back to its initial state if nothing new if found after that number of mutations (this matches the behavior of libFuzzer.) This is related to #47090.

Requesting a freeze exception, since this isn't a bug but has a significant impact on the efficiency/performance of the fuzzing engine, and has little risk.

cc @golang/release
@rolandshoemaker rolandshoemaker added this to the Go1.18 milestone Nov 16, 2021
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Change https://golang.org/cl/364214 mentions this issue: internal/fuzz: limit number of consecutive mutations

@stevenjohnstone stevenjohnstone mentioned this issue Nov 16, 2021
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@dr2chase
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@dmitshur @toothrot @cagedmantis are y'all the keeper(s) of freeze exceptions?
(It looks reasonable to me, it's a serious performance/usability problem)

@dmitshur
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dmitshur commented Nov 17, 2021 •
edited

Yes, we've discussed this on the release team. Thanks for letting us know. We don't have objections to this since it's a part of a feature that's already in scope for 1.18, and this change is based on new data from testing/experience. (And we're still relatively early in the freeze period—before beta 1.)

If the fuzzing team would like to proceed with this change, please do proceed. I'll mark this request as a normal Go1.18 issue in scope of freeze by removing the "[freeze exception]" suffix—but thanks again for letting us know about this.

@dmitshur dmitshur added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Nov 17, 2021
@dmitshur dmitshur changed the title internal/fuzz: limit the number of consecutive mutations applied to an input [freeze exception] internal/fuzz: limit the number of consecutive mutations applied to an input Nov 17, 2021
@dmitshur dmitshur added the fuzz Issues related to native fuzzing support label Nov 17, 2021
@dmitshur dmitshur added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Nov 18, 2021
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FrozenDueToAge fuzz Issues related to native fuzzing support NeedsFix The path to resolution is known, but the work has not been done.
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Go Security
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Go1.18
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@dmitshur @dr2chase @rolandshoemaker @gopherbot