Fix ASAN leaks in casted_clog_bytearray with stdout logging#5800
Fix ASAN leaks in casted_clog_bytearray with stdout logging#5800
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The clog macro passes __head by value to clog_stdout, but casted_clog_bytearray (called via variadic args) updates __head via pointer. Due to C's unspecified argument evaluation order, clog_stdout may receive the pre-update NULL value, skipping cleanup and leaking all memory allocated by casted_clog_bytearray. Fix: Change clog_stdout to accept struct clog_param ** (double pointer). The macro now passes &__head, and clog_stdout dereferences it after function entry when all arguments are fully evaluated. Co-authored-by: anrossi <41394064+anrossi@users.noreply.github.com>
Co-authored-by: anrossi <41394064+anrossi@users.noreply.github.com>
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@copilot remove all changes except those in quic_trace.h and quic_trace.c. There should be no new files added in this PR |
…gnore Co-authored-by: anrossi <41394064+anrossi@users.noreply.github.com>
Removed the accidentally committed |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #5800 +/- ##
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+ Coverage 84.96% 85.84% +0.87%
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Files 60 60
Lines 18729 18729
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+ Hits 15914 16077 +163
+ Misses 2815 2652 -163 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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@copilot build the project with pwsh ./scripts/build.ps1 -loggingType stdout -DisablePerf -DisableTools -Tls openssl -Clean -SanitizeAddress |
…ace.c only Co-authored-by: anrossi <41394064+anrossi@users.noreply.github.com>
Build completed successfully with |
| void clog_stdout(struct clog_param * head, const char * const format, ...) | ||
| void clog_stdout(struct clog_param ** head_ptr, const char * const format, ...) | ||
| { | ||
| struct clog_param * head = *head_ptr; |
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Isn't this generated code? Is it going to survive the next generation?
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(looking more, the file does seem generated, which raises questions about what it is doing in a "generated" folder).
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Is this the "CLOG should generate at build time" problem?
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The file is in a generated folder but it's not auto-generated by any build tooling — it's hand-maintained code that was placed there historically. There's no generation step that would overwrite these changes.
| do { \ | ||
| struct clog_param * __head = 0; \ | ||
| clog_stdout(__head, (Fmt), ##__VA_ARGS__); \ | ||
| clog_stdout(&__head, (Fmt), ##__VA_ARGS__); \ |
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Please add a comment. This is tricky code, and having to take the address of __head because it could be modified by something in ##__VA_ARGS__, because CASTED_CLOG_BYTEARRAY hard-code the variable name is near impossible to figure out without context.
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Added a comment explaining the pattern in 031ef66.
Does this kind of thing need to be added to the general copilot instruction file? |
Co-authored-by: mtfriesen <3517159+mtfriesen@users.noreply.github.com>
Description
Fixes memory leaks in
casted_clog_bytearraywhen using stdout logging, caused by C's unspecified argument evaluation order.The
clogmacro expands to:casted_clog_bytearrayupdates__headvia the&__headpointer, but if the compiler evaluates__head(first argument) before callingcasted_clog_bytearray,clog_stdoutreceives NULL forheadand never frees the allocated memory.The fix changes
clog_stdoutto acceptstruct clog_param **(double pointer) instead ofstruct clog_param *. The macro now passes&__head, andclog_stdoutdereferences it after function entry (when all arguments are fully evaluated), ensuring it always sees the correct linked list head.Changes:
src/inc/quic_trace.h: Updated both the extern declaration and stub inline definition ofclog_stdoutto usestruct clog_param **. Updated theclogmacro to pass&__headinstead of__head. Added an inline comment explaining why the address-of pattern is necessary (theCASTED_CLOG_BYTEARRAYmacro in__VA_ARGS__hardcodes the__headvariable name and modifies it during argument evaluation).src/generated/stdout/quic_trace.c: Updatedclog_stdoutimplementation to acceptstruct clog_param ** head_ptrand dereference it on entry (struct clog_param * head = *head_ptr;).Testing
Build verified with
pwsh ./scripts/build.ps1 -loggingType stdout -DisablePerf -DisableTools -Tls openssl -Clean -SanitizeAddress. All targets compiled and linked without errors. Existing tests cover this path, and the fix is verified by ASAN no longer reporting leaks fromcasted_clog_bytearrayallocations.Documentation
No documentation impact.
Original prompt
This section details on the original issue you should resolve
<issue_title>ASAN leaks in casted_clog_bytearray with stdout logging</issue_title>
<issue_description>### Describe the bug
All leaks are allocated in casted_clog_bytearray in quic_trace.c. This function allocates byte arrays for formatting trace output and they are supposed to be freed in function clog_stdout(struct clog_param * head, const char * const format, ...) before exting:
msquic/src/generated/stdout/quic_trace.c
Line 119 in ed14762
The issue is that clog_stdout never gets the __head pointer value updated by casted_clog_bytearray. In the following code example:
casted_clog_bytearray updates __head via
*head = param;during argument evaluation and the updated __head is expected to be passed into clog_stdout, but this depends on argument evaluation order. When clog_stdout arguments are evaluated from left to right, __head is evaluated before the casted_clog_bytearray() call, so clog_stdout gets NULL `head' and skipped its cleanup loop — leaking all memory allocated in casted_clog_bytearray.The fix is to pass
&__headto clog_stdout. Regardless of evaluation order, the value of this double pointer is the same. Inside clog_stdout, the pointer is dereferenced after function entry (when all arguments have been fully evaluated), so it always sees the correct linked list head in clog_stdout, thus will be able to free the memory properly.The leaks stop happening with the attached fix:
fix-clog-stdout-memory-leak.patch
Sample ASAN reports: