Bug #22471: Thread#name= on a terminated thread may dump core

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED

[mame (Yusuke Endoh)]

Calling Thread#name= on a terminated thread calls pthread_setname_np() with an invalid pthread_t, which can cause a SEGV or rename an unrelated thread.

ts = 100.times.map { Thread.new {} }.each(&:join)
ts.each { |t| t.name = "x" }

$ ruby -v test.rb
ruby 4.1.0dev (2026-08-21T07:50:27Z master c9e9101403) +PRISM [x86_64-linux]
test.rb:2: [BUG] Segmentation fault at 0x0000716a88eae990

[mame (Yusuke Endoh)]

https://github.com/ruby/ruby/pull/19520

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

Applied in changeset git|6fdd4520878eebd737d2a702c62051d46f199f89.

---

Skip setting the native thread name of a terminated thread

The native thread of a terminated thread may have already exited, so
its pthread_t is no longer valid. Passing it to pthread_setname_np()
could crash or rename an unrelated thread.

[Bug #22471]

Co-Authored-By: Claude Opus 5.5 [e-mail]