[mono] Prevent memory corruption when decoding UCO entry point #86266
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ivanpovazan
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vargaz,
lambdageek and
SamMonoRT
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ghost
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the
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/azp run runtime-extra-platforms |
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Azure Pipelines successfully started running 1 pipeline(s). |
vargaz
approved these changes
May 15, 2023
filipnavara
reviewed
May 15, 2023
| @@ -5352,10 +5352,16 @@ MONO_RESTORE_WARNING | |||
| for (j = 0; j < decoded_args->named_args_num; ++j) { | |||
| if (decoded_args->named_args_info [j].field && !strcmp (decoded_args->named_args_info [j].field->name, "EntryPoint")) { | |||
| named = (const char *)decoded_args->named_args[j]->value.primitive; | |||
| slen = mono_metadata_decode_value (named, &named) + (int)strlen(acfg->user_symbol_prefix); | |||
| export_name = (char *)g_malloc (slen + 1); | |||
| sprintf (export_name, "%s%s", acfg->user_symbol_prefix, named); | |||
There was a problem hiding this comment.
FWIW this could have been modified to
namedlen = mono_metadata_decode_value (named, &named);
slen = namedlen + (int)strlen(acfg->user_symbol_prefix);
export_name = (char *)g_malloc (slen + 1);
sprintf (export_name, "%s%.*s", acfg->user_symbol_prefix, namedlen, named);(+ declaration of namedlen)
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Thank you for your suggestion.
However, even though it achieves the same thing, I prefer not to use sprintf as originally it hid the underlying problem that was difficult to track down. So for that reason, I will keep it as is (simple and easily debuggable).
lambdageek
approved these changes
May 15, 2023
This was referenced May 16, 2023
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Failures are known and unrelated. |
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Description
This PR fixes an issue with memory corruption when MonoAOT compiler decodes the name of the exported symbols specified via
EntryPointof aUnmanagedCallersOnlymethod.The offending lines were assuming that the entry point string in the metadata blob is null terminated, which caused
sprintfto corrupt the memory aroundexport_name.I haven't been able to reproduce the issue with a smaller example other than how it is described in the tracking issue. If I manage to find a simple repro, I will add a unit test.
PS Not sure how this was not noticed before. One possibility is that the UCOs causing the problem have different encoding in the metadata blob, as they are generated by Cecil library not Roslyn.
Fixes #86264