[glibc] hurd: Don't leak __hurd_reply_port0

[glibc] hurd: Don't leak __hurd_reply_port0

[Samuel Thibault]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=cd019ddd892e182277fadd6aedccc57fa3923c8d

commit cd019ddd892e182277fadd6aedccc57fa3923c8d
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Sun Mar 19 18:10:10 2023 +0300

    hurd: Don't leak __hurd_reply_port0
    
    Previously, once we set up TLS, we would implicitly switch from using
    __hurd_reply_port0 to reply_port inside the TCB, leaving the former
    unused. But we never deallocated it, so it got leaked.
    
    Instead, migrate the port into the new TCB's reply_port slot. This
    avoids both the port leak and an extra syscall to create a new reply
    port for the TCB.
    
    Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
    Message-Id: <20230319151017.531737-28-bugaevc@gmail.com>

Diff:
---
 sysdeps/mach/hurd/i386/tls.h   | 5 +++++
 sysdeps/mach/hurd/x86_64/tls.h | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/sysdeps/mach/hurd/i386/tls.h b/sysdeps/mach/hurd/i386/tls.h
index ee7b8004bc..0ac8917a95 100644
--- a/sysdeps/mach/hurd/i386/tls.h
+++ b/sysdeps/mach/hurd/i386/tls.h
@@ -141,12 +141,15 @@ _hurd_tls_init (tcbhead_t *tcb)
   HURD_TLS_DESC_DECL (desc, tcb);
   thread_t self = __mach_thread_self ();
   bool success = true;
+  extern mach_port_t __hurd_reply_port0;
 
   /* This field is used by TLS accesses to get our "thread pointer"
      from the TLS point of view.  */
   tcb->tcb = tcb;
   /* We always at least start the sigthread anyway.  */
   tcb->multiple_threads = 1;
+  /* Take over the reply port we've been using.  */
+  tcb->reply_port = __hurd_reply_port0;
 
   /* Get the first available selector.  */
   int sel = -1;
@@ -172,6 +175,8 @@ _hurd_tls_init (tcbhead_t *tcb)
 
   /* Now install the new selector.  */
   asm volatile ("mov %w0, %%gs" :: "q" (sel));
+  /* This port is now owned by the TCB.  */
+  __hurd_reply_port0 = MACH_PORT_NULL;
 
 out:
   __mach_port_deallocate (__mach_task_self (), self);
diff --git a/sysdeps/mach/hurd/x86_64/tls.h b/sysdeps/mach/hurd/x86_64/tls.h
index da504d9c81..2b7135f635 100644
--- a/sysdeps/mach/hurd/x86_64/tls.h
+++ b/sysdeps/mach/hurd/x86_64/tls.h
@@ -177,13 +177,20 @@ _hurd_tls_init (tcbhead_t *tcb)
 {
   error_t err;
   thread_t self = __mach_thread_self ();
+  extern mach_port_t __hurd_reply_port0;
 
   /* We always at least start the sigthread anyway.  */
   tcb->multiple_threads = 1;
+  /* Take over the reply port we've been using.  */
+  tcb->reply_port = __hurd_reply_port0;
 
   err = _hurd_tls_new (self, tcb);
   if (err == 0)
-    __libc_tls_initialized = 1;
+    {
+      __libc_tls_initialized = 1;
+      /* This port is now owned by the TCB.  */
+      __hurd_reply_port0 = MACH_PORT_NULL;
+    }
   __mach_port_deallocate (__mach_task_self (), self);
   return err == 0;
 }