config_format: cf_yaml: fix Windows crash when libyaml is loaded as DLL #11402

bp-cheng · 2026-01-27T04:59:10Z

On Windows, passing FILE* across DLL boundaries can cause crashes
due to different C runtime libraries having incompatible internal
FILE structures.

When libyaml is built as a dynamic library (DLL), using
yaml_parser_set_input_file() causes the FILE* pointer to cross
the DLL boundary, leading to memory corruption or crashes.

This fix reads the YAML config file into a memory buffer and uses
yaml_parser_set_input_string() instead of yaml_parser_set_input_file(),
avoiding the cross-DLL FILE* issue.

The implementation opens the file in binary mode ("rb") for consistent
behavior, reads the entire file content into a buffer, uses
yaml_parser_set_input_string() with the buffer, and properly frees
the buffer after parsing.

Signed-off-by: BP Cheng bp_cheng@hotmail.com

Summary by CodeRabbit

Bug Fixes
- YAML configuration loading now reads files into memory first for more reliable include handling and cross-platform safety.
- Improved error reporting with clearer line/column context and hints to pinpoint offending YAML.
- Stronger resource management and centralized cleanup to avoid leaks and handle read/parsing failures gracefully.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

On Windows, passing FILE* across DLL boundaries can cause crashes due to different C runtime libraries having incompatible internal FILE structures. When libyaml is built as a dynamic library (DLL), using yaml_parser_set_input_file() causes the FILE* pointer to cross the DLL boundary, leading to memory corruption or crashes. This fix reads the YAML config file into a memory buffer and uses yaml_parser_set_input_string() instead of yaml_parser_set_input_file(), avoiding the cross-DLL FILE* issue. The implementation opens the file in binary mode ("rb") for consistent behavior, reads the entire file content into a buffer, uses yaml_parser_set_input_string() with the buffer, and properly frees the buffer after parsing. Signed-off-by: BP Cheng <bp_cheng@hotmail.com> Signed-off-by: BP Cheng <bp_cheng@hotmail.com>

bp-cheng · 2026-01-27T04:59:30Z

@codex

coderabbitai · 2026-01-27T05:00:09Z

📝 Walkthrough

Walkthrough

Reads YAML include files into an in-memory buffer and feeds that buffer to the YAML parser (yaml_parser_set_input_string) instead of using yaml_parser_set_input_file; opens files in binary mode (rb), adds buffer allocation/validation and null-termination, improves parse error diagnostics, and adds deterministic cleanup and Windows DLL-safe behavior. (50 words)

Changes

Cohort / File(s)	Summary
YAML Config Buffer Input `src/config_format/flb_cf_yaml.c`	Replace FILE-based input with buffer-based parsing via `yaml_parser_set_input_string()`; open include files in binary mode (`rb`); add file size detection, buffer allocation & null-termination, read-error handling, early FILE close, conditional parser/event deletion, centralized `done` cleanup path, and richer YAML parse error reporting (line/column and contextual hints).

Sequence Diagram

sequenceDiagram
    participant FS as File System
    participant Buffer as Buffer Manager
    participant Parser as YAML Parser

    FS->>Buffer: open include file (`rb`)
    Buffer->>Buffer: stat/determine file size & allocate buffer
    FS->>Buffer: read file contents into buffer
    Buffer->>Buffer: null-terminate & validate read length
    Buffer->>FS: close FILE* (early close for Windows DLL safety)
    Buffer->>Parser: yaml_parser_set_input_string(buffer, size)
    Parser->>Parser: parse YAML from memory buffer
    Parser-->>Buffer: parsing result (success / failure + problem details)
    Buffer->>Buffer: free allocated buffer
    Parser->>Parser: delete parser if initialized

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

config_format: yaml: fix state parameter for read_blob in Windows #10915 — Related Windows include-file handling changes.

Suggested labels

backport to v4.2.x

Suggested reviewers

edsiper

Poem

🐰 I nibble bytes from file to heap,
Pack them snug where parsers sleep,
Closed the handle, cleaned my tracks,
Fed the YAML, then hopped back,
Buffer freed — the rabbit's leap.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately describes the main change: fixing a Windows crash by switching from FILE* (yaml_parser_set_input_file) to buffer-based input (yaml_parser_set_input_string) when libyaml is loaded as a DLL.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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src/config_format/flb_cf_yaml.c

On Windows, passing FILE* across DLL boundaries can cause crashes due to different C runtime libraries having incompatible internal FILE structures. When libyaml is built as a dynamic library (DLL), using yaml_parser_set_input_file() causes the FILE* pointer to cross the DLL boundary, leading to memory corruption or crashes. This fix reads the YAML config file into a memory buffer and uses yaml_parser_set_input_string() instead of yaml_parser_set_input_file(), avoiding the cross-DLL FILE* issue. The implementation opens the file in binary mode ("rb") for consistent behavior, reads the entire file content into a buffer, uses yaml_parser_set_input_string() with the buffer, and properly frees the buffer after parsing. Error paths now use goto to ensure proper cleanup of parser state and ctx->level. Signed-off-by: BP Cheng <bp_cheng@hotmail.com> Signed-off-by: BP Cheng <bp_cheng@hotmail.com>

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/config_format/flb_cf_yaml.c`:
- Around line 2963-2971: After calling fread(file_buffer, 1, file_size, fh)
check ferror(fh) (and/or compare bytes_read to file_size as desired) before
closing fh; on error free file_buffer, close fh if open, and return/propagate an
error instead of proceeding. For yaml_parser_initialize(&parser) capture its
return value and only set parser_initialized = 1 when it returns non-zero; if it
fails, free file_buffer, close fh if needed and return an error without calling
yaml_parser_delete or yaml_parser_set_input_string. Reference symbols: fread,
fh, file_buffer, file_size, bytes_read, yaml_parser_initialize,
parser_initialized, yaml_parser_set_input_string, yaml_parser_delete.

src/config_format/flb_cf_yaml.c

On Windows, passing FILE* across DLL boundaries can cause crashes due to different C runtime libraries having incompatible internal FILE structures. When libyaml is built as a dynamic library (DLL), using yaml_parser_set_input_file() causes the FILE* pointer to cross the DLL boundary, leading to memory corruption or crashes. This fix reads the YAML config file into a memory buffer and uses yaml_parser_set_input_string() instead of yaml_parser_set_input_file(), avoiding the cross-DLL FILE* issue. The implementation opens the file in binary mode ("rb") for consistent behavior, reads the entire file content into a buffer, uses yaml_parser_set_input_string() with the buffer, and properly frees the buffer after parsing. Error paths now use goto to ensure proper cleanup of parser state and ctx->level. Added error checks for fread (via ferror) and yaml_parser_initialize return values. Signed-off-by: BP Cheng <bp_cheng@hotmail.com> Signed-off-by: BP Cheng <bp_cheng@hotmail.com>

coderabbitai

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/config_format/flb_cf_yaml.c (1)
2840-2841: Guard yaml_event_delete() for early-error paths before parser loop.

When early errors occur (file size check, malloc failure, parser initialization failure at lines 2980-2981), goto done is executed before any yaml_parser_parse() call. The event at line 2840 remains uninitialized, but unconditional yaml_event_delete(&event) at line 3035 violates libyaml's API contract: yaml_event_delete() must only be called after a successful yaml_parser_parse() call. Initialize event and track successful parse execution to guard the delete.
🐛 Proposed fix

Initialize event and only delete after confirmed successful parse:
-    yaml_event_t event;
+    yaml_event_t event = {0};
     FILE *fh;
And guard the cleanup delete:
-    if (code == -1) {
-        yaml_event_delete(&event);
-    }
+    if (code == -1 && event.type != YAML_NO_EVENT) {
+        yaml_event_delete(&event);
+    }
Or more robustly, only delete if the loop was entered and a parse completed successfully.

bp-cheng · 2026-01-27T05:56:48Z

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src/config_format/flb_cf_yaml.c

On Windows, passing FILE* across DLL boundaries can cause crashes due to different C runtime libraries having incompatible internal FILE structures. When libyaml is built as a dynamic library (DLL), using yaml_parser_set_input_file() causes the FILE* pointer to cross the DLL boundary, leading to memory corruption or crashes. This fix reads the YAML config file into a memory buffer and uses yaml_parser_set_input_string() instead of yaml_parser_set_input_file(), avoiding the cross-DLL FILE* issue. The implementation opens the file in binary mode ("rb") for consistent behavior, reads the entire file content into a buffer, uses yaml_parser_set_input_string() with the buffer, and properly frees the buffer after parsing. Signed-off-by: BP Cheng <bp_cheng@hotmail.com> Signed-off-by: BP Cheng <bp_cheng@hotmail.com>

bp-cheng requested review from cosmo0920 and edsiper as code owners January 27, 2026 04:59

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config_format: cf_yaml: fix Windows crash when libyaml is loaded as DLL #11402

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Sequence Diagram

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