| Summary: | SIGSEGV in musl freelocale | ||
|---|---|---|---|
| Product: | [Developer tools] valgrind | Reporter: | shininggate83 |
| Component: | general | Assignee: | Julian Seward <jseward> |
| Status: | RESOLVED NOT A BUG | ||
| Severity: | normal | CC: | mark, pjfloyd, sam |
| Priority: | NOR | ||
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Platform: | Other | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed In: | ||
| Sentry Crash Report: | |||
| Attachments: |
minimal test case
patch replacing __libc_free |
||
Created attachment 142799 [details]
patch replacing __libc_free
Although it might be an idea to intercept __libc_free (but then also __libc_malloc) it seems you uncovered a bug in musl. newlocale and freelocale do use __libc_malloc and __libc_free, but duplocale uses malloc. That means locales created by duplocale can use a different malloc allocator than the internal one. This bug would also show up if you used another LD_PRELOAD malloc ELF interposition tool. I agree with Mark. We shouldn't put bug workarounds in Valgrind unless really necessary. I think this was fixed in musl by https://git.musl-libc.org/cgit/musl/commit/?id=6d8a515796270eb6cec8a278cb353a078a10f09a. Yes looks like it is fixed in musl. |
Created attachment 142798 [details] minimal test case SUMMARY When running the program `min.c` under valgrind and musl libc, the process is terminated with SIGSEGV in `freelocale`. STEPS TO REPRODUCE 1. Compile and run `min.c` with valgrind using musl libc. OBSERVED RESULT Program crashes with SIGSEGV. EXPECTED RESULT No crashes. SOFTWARE/OS VERSIONS Linux 5.10.75, Alpine Linux, musl 1.2.2 ADDITIONAL INFORMATION The issue seems to be that musl calls `__libc_free` in freelocale, which valgrind does not replace, leading to musl trying to read metadata that is not present, instead getting garbage. In glibc, freelocale calls the normal `free` function, which is correctly replaced by valgrind. Attached is a (semi-)tested patch which replaces `__libc_free`, making the test case and the original application run fine.