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Between v1.4.1 and v1.5.1.1, 6793d14 added a GC mark function to the `SyckNode` Data wrapper created inside `rb_syck_load_handler`. The change fixed one crash (GC collecting node children mid-parse) but opened a new one: the parser frees the node the moment the handler returns, so any later GC that still reaches the wrapper, via a conservative stack root, calls the mark function on a dangling pointer.
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While working on ruby#54, I found that ASAN flags this line because this function call tries to read 53 bytes of a 50-byte string. That's not right!
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Strangely I had the same fix from Claude only a few days ago. The test program i wrote ran ok, but not had time to check this out in the main product yet. In my testing I found the check for n being null "if ( n == NULL ) return;" didn't seem to be required but there is no harm in it. |
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Disclaimer: this patch was written with the assistance of a large language model (Claude Opus 4.7 with 1M context). I am very unfamiliar with C, so it's completely possible that it has made any number of mistakes.
Between v1.4.1 and v1.5.1.1, #40 added a GC mark function to the
SyckNodeData wrapper created insiderb_syck_load_handler. The change fixed one crash (GC collecting node children mid-parse) but opened a new one: the parser frees the node the moment the handler returns, so any later GC that still reaches the wrapper, via a conservative stack root, calls the mark function on a dangling pointer.Possibly fixes #50 (it gets rid of it in my testing, but it's possible this has other implications I haven't thought of, or is only a partial fix)
cc @peterzhu2118
Resources used while making this PR: https://gist.github.com/RDIL/5e2bda4041ed3b804449472a9bf7d809
Note: build is blocked on #56