Patchwork yet another memory leak, in dlfcn this time

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Submitter DJ Delorie
Date April 5, 2018, 5:32 a.m.
Message ID <xn6056jk0a.fsf@greed.delorie.com>
Download mbox | patch
Permalink /patch/26610/
State New
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Comments

DJ Delorie - April 5, 2018, 5:32 a.m.
While doing the work on extracting the malloc hooks, I discovered
another place where memory needs to be free'd for leak checkers.
Unable to reproduce with valgrind but that might just mean valgrind
uses a different technique to interpose the calls.  This one triggers
if you call dlfcn() during LD_PRELOAD.

The hook might be a bit hacky, but then again, all the freeres hook
stuff is a bit hacky.


	* dlfcn/Makefile: Add dlfreeres and libc_dlfreeres.
	* dlfcn/Versions: Add __libdl_freeres as GLIBC_PRIVATE.
	* dlfcn/dlerror.c (dlerror_main_freeres): New.
	* dlfcn/dlfreeres.c: New.
	* dlfcn/sdlfreeres.c: New.
	* malloc/set-freeres.c: Add hook for libdl.so

Patch

diff --git a/dlfcn/Makefile b/dlfcn/Makefile
index 56dcae0604..34f9923334 100644
--- a/dlfcn/Makefile
+++ b/dlfcn/Makefile
@@ -22,7 +22,7 @@  include ../Makeconfig
 headers		:= bits/dlfcn.h dlfcn.h
 extra-libs	:= libdl
 libdl-routines	:= dlopen dlclose dlsym dlvsym dlerror dladdr dladdr1 dlinfo \
-		   dlmopen dlfcn
+		   dlmopen dlfcn dlfreeres
 routines	:= $(patsubst %,s%,$(filter-out dlfcn,$(libdl-routines)))
 elide-routines.os := $(routines)
 
diff --git a/dlfcn/Versions b/dlfcn/Versions
index 97902f0dfd..1df6925a92 100644
--- a/dlfcn/Versions
+++ b/dlfcn/Versions
@@ -13,5 +13,6 @@  libdl {
   }
   GLIBC_PRIVATE {
     _dlfcn_hook;
+    __libdl_freeres;
   }
 }
diff --git a/dlfcn/dlerror.c b/dlfcn/dlerror.c
index 04dce9ddc6..8111c69dcb 100644
--- a/dlfcn/dlerror.c
+++ b/dlfcn/dlerror.c
@@ -215,13 +215,27 @@  static void
 free_key_mem (void *mem)
 {
   check_free ((struct dl_action_result *) mem);
-
   free (mem);
   __libc_setspecific (key, NULL);
 }
 
 # ifdef SHARED
 
+void
+dlerror_main_freeres (void)
+{
+  void *mem;
+
+  mem = __libc_getspecific (key);
+
+  if (mem)
+    {
+      free (mem);
+      __libc_setspecific (key, NULL);
+    }
+}
+text_set_element (libdl_freeres_hooks, dlerror_main_freeres);
+
 struct dlfcn_hook *_dlfcn_hook __attribute__((nocommon));
 libdl_hidden_data_def (_dlfcn_hook)
 
diff --git a/dlfcn/dlfreeres.c b/dlfcn/dlfreeres.c
new file mode 100644
index 0000000000..567630a2e6
--- /dev/null
+++ b/dlfcn/dlfreeres.c
@@ -0,0 +1,23 @@ 
+/* Clean up allocated libdl memory on demand.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <set-hooks.h>
+
+DEFINE_HOOK (libdl_freeres_hooks, (void))
+
+DEFINE_HOOK_RUNNER (libdl_freeres_hooks, __libdl_freeres, (void), ())
diff --git a/dlfcn/sdlfreeres.c b/dlfcn/sdlfreeres.c
new file mode 100644
index 0000000000..7347672990
--- /dev/null
+++ b/dlfcn/sdlfreeres.c
@@ -0,0 +1 @@ 
+#include "dlfreeres.c"
diff --git a/malloc/set-freeres.c b/malloc/set-freeres.c
index f4a0e7bda4..a74f6bd54b 100644
--- a/malloc/set-freeres.c
+++ b/malloc/set-freeres.c
@@ -26,6 +26,8 @@  DEFINE_HOOK (__libc_subfreeres, (void));
 
 symbol_set_define (__libc_freeres_ptrs);
 
+extern __attribute__((weak)) void __libdl_freeres (void);
+
 void __libc_freeres_fn_section
 __libc_freeres (void)
 {
@@ -41,6 +43,10 @@  __libc_freeres (void)
 
       RUN_HOOK (__libc_subfreeres, ());
 
+      /* This hooks into libdl.so's table of things-to-be-freed.  */
+      if (__libdl_freeres)
+	__libdl_freeres ();
+
       for (p = symbol_set_first_element (__libc_freeres_ptrs);
            !symbol_set_end_p (__libc_freeres_ptrs, p); ++p)
         free (*p);