If libthr.so is dlopened without RTLD_GLOBAL flag, the libthr symbols

do not participate in the global symbols namespace, but rtld locks are
still replaced and functions are interposed.  In particular,
__pthread_map_stacks_exec is resolved to the libc version.  If a
library is loaded later, which requires adjustment of the stack
protection mode, rtld calls into libc __pthread_map_stacks_exec due to
the symbols scope.  The libc version might recurse into binder and
recursively acquire rtld bind lock, causing the hang.

Make libc __pthread_map_stacks_exec() interposed, which synchronizes
rtld locks and version of the stack exec hook when libthr loaded,
regardless of the symbol scope control or symbol resolution order.

The __pthread_map_stacks_exec() symbol is removed from the private
version in libthr since libc symbol now operates correctly in presence
of libthr.

Reported and tested by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

1 files changed, 1 insertions, 2 deletions

diff --git a/lib/libthr/thread/thr_stack.c b/lib/libthr/thread/thr_stack.c
index e5d149e..74e1329 100644
--- a/lib/libthr/thread/thr_stack.c
+++ b/lib/libthr/thread/thr_stack.c
@@ -161,9 +161,8 @@ singlethread_map_stacks_exec(void)
 	    rlim.rlim_cur, _rtld_get_stack_prot());
 }
 
-void __pthread_map_stacks_exec(void);
 void
-__pthread_map_stacks_exec(void)
+__thr_map_stacks_exec(void)
 {
 	struct pthread *curthread, *thrd;
 	struct stack *st;