If a shared library (so) is loaded using dlopen and utilizes thread-local storage (TLS), the memory will not be freed upon thread exit, resulting in a memory leak.

This issue has been resolved in glibc-2.14. However, it remains unresolved in uClibc.

The following patch is based on the patch made in glibc and has been validated as effective on the x86-64 architecture.

 

diff --git a/libpthread/nptl/allocatestack.c b/libpthread/nptl/allocatestack.c

index 7ef884543..941ef22f0 100644

--- a/libpthread/nptl/allocatestack.c

+++ b/libpthread/nptl/allocatestack.c

@@ -24,6 +24,7 @@

 #include <unistd.h>

 #include <sys/mman.h>

 #include <sys/param.h>

+#include <dl-tls.h>

 #include <tls.h>

 #include <lowlevellock.h>

 #include <link.h>

@@ -241,6 +242,10 @@ get_cached_stack (size_t *sizep, void **memp)

 

   /* Clear the DTV.  */

   dtv_t *dtv = GET_DTV (TLS_TPADJ (result));

+  for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)

+    if (! dtv[1 + cnt].pointer.is_static

+             && dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)

+      free (dtv[1 + cnt].pointer.val);

   memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));

 

   /* Re-initialize the TLS.  */

diff --git a/libpthread/nptl/sysdeps/generic/dl-tls.c b/libpthread/nptl/sysdeps/generic/dl-tls.c

index 7d25e4706..7b7991be8 100644

--- a/libpthread/nptl/sysdeps/generic/dl-tls.c

+++ b/libpthread/nptl/sysdeps/generic/dl-tls.c

@@ -45,8 +45,6 @@

    to allow dynamic loading of modules defining IE-model TLS data.  */

 # define TLS_STATIC_SURPLUS    64 + DL_NNS * 100

 

-/* Value used for dtv entries for which the allocation is delayed.  */

-# define TLS_DTV_UNALLOCATED   ((void *) -1l)

 

 #ifndef SHARED

 extern dtv_t static_dtv;

diff --git a/libpthread/nptl/sysdeps/x86_64/dl-tls.h b/libpthread/nptl/sysdeps/x86_64/dl-tls.h

index d6c338cda..5cac55f33 100644

--- a/libpthread/nptl/sysdeps/x86_64/dl-tls.h

+++ b/libpthread/nptl/sysdeps/x86_64/dl-tls.h

@@ -26,3 +26,6 @@ typedef struct

 

 

 extern void *__tls_get_addr (tls_index *ti);

+

+/* Value used for dtv entries for which the allocation is delayed.  */

+#define TLS_DTV_UNALLOCATED    ((void *) -1l)

 

 

 

 

Ref:    

https://sourceware.org/bugzilla/show_bug.cgi?id=12650

 

 

How to reproduce: