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Message-ID: <62be4b85-4a42-413e-a83f-866eab4d601a@gmail.com>
Date: Tue, 2 Feb 2021 23:04:23 -0500
From: Dominic Chen <d.c.ddcc@...il.com>
To: musl@...ts.openwall.com
Subject: Incorrect thread TID caching
I've been debugging a local port of Chrome using musl, and have noticed
that musl is caching the thread TID in __pthread_self()->tid, which
results in incorrect behavior if the application calls the clone() libc
wrapper or the clone system call, and then calls libc functions which
use the cached TID value, like raise().
From a quick skim of other libc implementations, both bionic and glibc
don't seem to cache TID, and directly call the gettid system call inside
raise(). I also recall that glibc removed PID caching a few years ago
due to similar issues there as well. So, it seems that musl should
either not cache the TID, or at least update the cached value after
returning from the system call inside the clone() wrapper (with special
handling for CLONE_VM/CLONE_VFORK)?
Please CC me on replies.
Thanks,
Dominic
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