From 84ebec6ceea997568c1711e7d810ad6bb3a96346 Mon Sep 17 00:00:00 2001 From: Samuel Holland Date: Sun, 30 Jun 2019 22:44:28 -0500 Subject: [PATCH] fix deadlock in synccall after threaded fork synccall may be called by AS-safe functions such as setuid/setgid after fork. although fork() resets libc.threads_minus_one, causing synccall to take the single-threaded path, synccall still takes the thread list lock. This lock may be held by another thread if for example fork() races with pthread_create(). After fork(), the value of the lock is meaningless, so clear it. maintainer's note: commit 8f11e6127fe93093f81a52b15bb1537edc3fc8af and e4235d70672d9751d7718ddc2b52d0b426430768 introduced this regression. the state protected by this lock is the linked list, which is entirely replaced in the child path of fork (next=prev=self), so resetting it is semantically sound. --- src/process/fork.c | 1 + 1 file changed, 1 insertion(+) diff --git a/src/process/fork.c b/src/process/fork.c index 11286ef4..fb42478a 100644 --- a/src/process/fork.c +++ b/src/process/fork.c @@ -28,6 +28,7 @@ pid_t fork(void) self->robust_list.off = 0; self->robust_list.pending = 0; self->next = self->prev = self; + __thread_list_lock = 0; libc.threads_minus_1 = 0; } __restore_sigs(&set); -- 2.25.1