提交: ae56f3a633860a984d42dd9a6959e1d5983296e5 - uclibc-ng (git)

Commit MetaInfo

• 修订版: ae56f3a633860a984d42dd9a6959e1d5983296e5 (tree)
• 时间: 2018-01-16 05:01:39
• 作者: Guo Ren <ren_guo@c-sk...>
• Commiter: Waldemar Brodkorb

Log Message

libpthread/nptl: bugfix malloc segfault in race conditions.

In libc/sysdeps/linux/common/bits/uClibc_pthread.h:
extern void weak_function _pthread_cleanup_push_defer(...)

This *weak_function* declaration will cause nptl/cleanup_defer_compat.c:
strong_alias (...) !!!FAIL!!!, because it include pthreadP.h->pthread.h
->uClibc_pthread.h

That means:
Readelf -s libpthread/nptl/cleanup_defer_compat.o you will get:
18: 00000000 198 FUNC WEAK DEFAULT 1 _pthread_cleanup_push_def
Readelf -s libc/misc/internals/uClibc_main.o you will also get:
32: 00000038 58 FUNC WEAK DEFAULT 1 _pthread_cleanup_push_def

Final: gcc malloc_pthread_test.c -lpthread
The libc/stdlib/malloc-standard/malloc.c:839 (MALLOC_LOCK->
_pthread_cleanup_push_def) will use the one in uClibc_main.o
!!!not in cleanup_defer_compat.o!!!, becasue two cleanup_defer_compat in
libc.a with the same weak declarations and the uClibc_main.o is close
to front.

All of malloc/free will failed in muti-threads' race conditions
probabilistic.

As it happens, uClibc-0.9.33.2 is OK, Becasue:
It's seperated in libpthread.a and libc.a, and the libc.a is the
last lib for ld internal-cmd, and malloc will get right cleanup_defer_compat
from libpthread.a.

This BUG is from 2016-09-24 to now:
>>>
commit 29ff9055c80efe77a7130767a9fcb3ab8c67e8ce
Author: Waldemar Brodkorb <[e-mail]>
Date: Sat Sep 24 02:55:31 2016 +0200

use a single libc and deduplicate threading code

Similar to musl libc a single libc has many benefits and solves
some open issues with uClibc-ng.

- no pthread_mutex_* weak symbols exported anymore
- applications no longer failing to link when either

-lrt or -lpthread are missing for dynamic and static linking mode

- smaller C library
- slightly better runtime performance

<<<

Perharps we need carefully check all of the impact about that commit.

Signed-off-by: Guo Ren <[e-mail]>

更改概述

• modified: libpthread/nptl/sysdeps/pthread/pthread.h

差异

--- a/libpthread/nptl/sysdeps/pthread/pthread.h
+++ b/libpthread/nptl/sysdeps/pthread/pthread.h
@@ -29,7 +29,7 @@
 #include <bits/pthreadtypes.h>
 #include <bits/setjmp.h>
 #include <bits/wordsize.h>
-#if defined _LIBC && ( defined IS_IN_libc || defined NOT_IN_libc )
+#if defined _LIBC && ( defined IS_IN_libc || !defined NOT_IN_libc )
 #include <bits/uClibc_pthread.h>
 #endif