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On 5/9/23 21:27, DJ Delorie wrote:
Great! Thanks for the links, I've done manual testing with the reproducer:Jarek Prokop <jprokop@xxxxxxxxxx> writes:Are the libffi/rebuilt packages available anywhere for us to experiment with?MPB uses COPR, so.. "before" builds: https://copr.fedorainfracloud.org/coprs/djdelorie/libffi-3.4.4.checker/ "after" builds: https://copr.fedorainfracloud.org/coprs/djdelorie/libffi-3.4.4/ ~~~ require 'fiddle/closure' require 'fiddle/struct' Fiddle::Closure.new(Fiddle::TYPE_VOID, []) fork { } GC.start ~~~ And with the copr build of libffi 3.4.4-3 , Ruby indeed no longer
crashes on this code. And it is great to see :)We have a reasonably reliable reproducer in Ruby [0] (also included in commit message [1]), but it is not executed as part of test suite,Yes, fork-without-exec case is a known "that should never have worked" case that only happens to work when your closure's backing store is also forked, which file-based mappings are *not*. You need either really old (rwx mmap, which security disables) or really new (static trampolines, which are r-x/rw- mmap'ed) libffi to support that. Hopefully that means your reproducers should not reproduce with the new libffi.Moreover, rebuild with current Ruby specfiles won't tell you much as we commented out the tests [2] to have less flaky builds. I'd recommend uncommenting the lines and run 5 to 10 builds (or just run any of the 2 reproducers).Well, if you comment out the tests, I have no way of knowing I broke anything, so have to rely on posting Change Requests and letting you let me know ;-) We are aware of this downside :/, we worked with relevant upstream, but a proper fix on the side of rubygem-fiddle would require nontrivial rewrite.Not saying you did anything wrong; if you have tests that pass or fail depending on system configurations outside your control, it's difficult to reliably test what you want to test. I'm just saying that when you disable tests, automated processes have no insight into those failures. (rubygem-ffi conversely has a closure pool that, AFAICT, prevents the issue altogether.) This was a long-running issue (read: spanning a few Fedora releases) and doing a rebuild 10 times to have 1 not segfault and go through the rest of the pipeline just for a teeny version rebase got really tiring. Thanks, Jarek Prokop |
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