From 36b72cd6fdfed2cac6b6ff1ed58a96d8265785cf Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 5 Oct 2022 10:41:30 -0400 Subject: fix potential deadlock in dlerror buffer handling at thread exit ever since commit 8f11e6127fe93093f81a52b15bb1537edc3fc8af introduced the thread list lock, this has been wrong. initially, it was wrong via calling free from the context with the thread list lock held. commit aa5a9d15e09851f7b4a1668e9dbde0f6234abada deferred the unsafe free but added a lock, which was also unsafe. in particular, it could deadlock if code holding freebuf_queue_lock was interrupted by a signal handler that takes the thread list lock. commit 4d5aa20a94a2d3fae3e69289dc23ecafbd0c16c4 observed that there was a lock here but failed to notice that it's invalid. there is no easy solution to this problem with locks; any attempt at solving it while still using locks would require the lock to be an AS-safe one (blocking signals on each access to the dlerror buffer list to check if there's deferred free work to be done) which would be excessively costly, and there are also lock order considerations with respect to how the lock would be handled at fork. instead, just use an atomic list. --- src/internal/fork_impl.h | 1 - 1 file changed, 1 deletion(-) (limited to 'src/internal') diff --git a/src/internal/fork_impl.h b/src/internal/fork_impl.h index 5892c13b..ae3a79e5 100644 --- a/src/internal/fork_impl.h +++ b/src/internal/fork_impl.h @@ -2,7 +2,6 @@ extern hidden volatile int *const __at_quick_exit_lockptr; extern hidden volatile int *const __atexit_lockptr; -extern hidden volatile int *const __dlerror_lockptr; extern hidden volatile int *const __gettext_lockptr; extern hidden volatile int *const __locale_lockptr; extern hidden volatile int *const __random_lockptr; -- cgit v1.2.1