https://bugs.llvm.org/show_bug.cgi?id=51407
Bug ID: 51407
Summary: Infinite loop in demangler
Product: tools
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: llvm-c++filt
Assignee: unassignedb...@nondot.org
Reporter: borisov.mikh...@gmail.com
CC: llvm-bugs@lists.llvm.org
A libfuzzer run has discovered some inputs for which the demangler does not
terminate.
When minimized, it looks like this: _Zcv1BIRT_EIS1_E
Deciphered:
_Z
cv - conversion operator
* result type
1B - "B"
I - template args begin
R - reference type <.
T_ - forward template reference | *
E - template args end | |
| |
* parameter type | |
I - template args begin | |
S1_ - substitution #1 * <'
E - template args end
The reason is: template-parameter refs in conversion operator result type
create forward-references, while substitutions are instantly resolved via
back-references. Together these can create a reference loop. It causes an
infinite loop in ReferenceType::collapse().
I see three possible ways to avoid these loops:
1. check if resolving a forward reference creates a loop and reject the invalid
input (hard to traverse AST at this point)
2. check if a substitution contains a malicious forward reference and reject
the invalid input (hard to traverse AST at this point; substitutions are quite
common: may affect performance; hard to clearly detect loops at this point)
3. detect loops in ReferenceType::collapse() (cannot reject the input)
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