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…, sun_path overflow Bug 1 - LxssHttpProxy.cpp: IPv6 substr extraction used wrong length calculation. substr(openBracket+1, closeBracket-1) is incorrect when openBracket > 0; fixed to substr(openBracket+1, closeBracket-openBracket-1). Also fixed empty-address guard to check closeBracket (not closeBracket-1). Bug 2 - LxssUserSession.cpp: Two instances of reinterpret_cast<HANDLE*> in ScopedMultiRelay construction should be reinterpret_cast<HANDLE> (without the pointer). Other identical callsites in the same file already use the correct cast. Bug 3 - LxssUserSession.cpp: GetLastError() was called unconditionally after CreateFileW, even on success. A stale ERROR_SHARING_VIOLATION from a prior API call could cause a false throw. Fixed to only check GetLastError() when CreateFileW fails (!vhd). Bug 4 - plan9.cpp: sun_path bounds check used > instead of >= leaving no room for null terminator. Also added a post-split check to ensure the child name fits after splitting parent/child for long paths.
benhillis
requested review from
Brian-Perkins,
OneBlue,
Copilot,
jstarks and
justus-camp-microsoft
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Pull request overview
This PR fixes four distinct bugs across three files related to incorrect string operations, type casting, error handling, and bounds checking.
Changes:
- Corrected IPv6 address extraction logic with proper substring bounds
- Fixed HANDLE type casting in relay construction
- Fixed premature GetLastError() call that could report stale errors
- Corrected bounds checking for Unix socket paths to ensure null terminator space
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/windows/service/exe/LxssHttpProxy.cpp | Fixed IPv6 address extraction substring calculation and empty address validation |
| src/windows/service/exe/LxssUserSession.cpp | Fixed HANDLE type casts and moved GetLastError() check to only execute on CreateFileW failure |
| src/linux/init/plan9.cpp | Fixed sun_path bounds check to account for null terminator and added validation after path splitting |
OneBlue
approved these changes
Feb 26, 2026
| return UnsupportedProxyReason::Supported; | ||
| } | ||
| portRemoved = portRemoved.substr(openBracket + 1, closeBracket - 1); | ||
| portRemoved = portRemoved.substr(openBracket + 1, closeBracket - openBracket - 1); |
Collaborator
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I wish there was an easy way to add test coverage for this.
If we ever factor IsUnsupportedProxy() in common I guess we could add coverage for this
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LxssHttpProxy.cpp: IPv6 substr extraction used wrong length calculation. substr(openBracket+1, closeBracket-1) is incorrect when openBracket > 0; fixed to substr(openBracket+1, closeBracket-openBracket-1). Also fixed empty-address guard to check closeBracket (not closeBracket-1).
LxssUserSession.cpp: Two instances of reinterpret_cast<HANDLE*> in ScopedMultiRelay construction should be reinterpret_cast (without the pointer). Other identical callsites in the same file already use the correct cast.
LxssUserSession.cpp: GetLastError() was called unconditionally after CreateFileW, even on success. A stale ERROR_SHARING_VIOLATION from a prior API call could cause a false throw. Fixed to only check GetLastError() when CreateFileW fails (!vhd).
plan9.cpp: sun_path bounds check used > instead of >= leaving no room for null terminator. Also added a post-split check to ensure the child name fits after splitting parent/child for long paths.