[uclibc-ng-devel] Re: TLS memory-leak with dlopen

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: