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Panic in regex_syntax, found by fuzzing #527

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PaulGrandperrin opened this issue Oct 15, 2018 · 1 comment
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Panic in regex_syntax, found by fuzzing #527

PaulGrandperrin opened this issue Oct 15, 2018 · 1 comment
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@PaulGrandperrin
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While fuzzing the regex_syntax target from https://github.com/rust-fuzz/targets, I hit this panic:

thread 'main' panicked at 'tried to unwrap expr from HirFrame, got: Group { old_flags: None }', /root/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-syntax-0.6.2/src/hir/translate.rs:203:18

Here is the regex:

regex::Regex::new("(((?x)))");

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@BurntSushi
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Nice! It looks like ((?x)) also panics. (?:(?x)) does as well. As does ((?x))x.

@BurntSushi BurntSushi added the bug label Oct 15, 2018
BurntSushi added a commit that referenced this issue Mar 30, 2019
@BurntSushi
syntax: fix bug when parsing ((?x))
ccfd843 
This fixes yet another bug with our handling of (?flags) directives in
the regex. This time, we try to be a bit more principled and
specifically treat a (?flags) directive as a valid empty sub-expression.
While this means we could remove errors reported from previous fixes for
things like `(?i)+`, we retain those for now since they are a bit weird.
Although `((?i))+` is now allowed, which is equivalent. We should
probably allow `(?i)+` in the future for consistency sake.

Fixes #527
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@BurntSushi @PaulGrandperrin