[PATCH] fclose does not remove FILE* from internal linked list

Denis Vlasenko vda.linux at googlemail.com
Sun Feb 4 18:54:21 UTC 2007


Hi there!

With certain combination of .config options fclose() does not
remove FILE* pointer from _stdio_openlist.  As a result, subsequent
fopen() may allocate new FILE structure exactly in place of one
freed by previous fclose(), which then makes _stdio_openlist
circularlt looped. The following program will enter infinite loop
trying to walk _stdio_openlist in exit():

#include <stdlib.h>
#include <stdio.h>
int main() {
        FILE* fp;
        fp = fopen("/etc/resolv.conf", "r");
        fclose(fp);
        fp = fopen("/etc/hosts", "r");
        exit(1);
}

"proof of concept" fix is:

libc/stdio/fclose.c

#ifdef __UCLIBC_MJN3_ONLY__
#warning REMINDER: inefficient - locks and unlocks twice and walks whole list
#endif
#if defined(__UCLIBC_HAS_THREADS__) && defined(__STDIO_BUFFERS)
        /* inefficient - locks/unlocks twice and walks whole list */
        __STDIO_OPENLIST_INC_DEL_CNT;
        __STDIO_OPENLIST_DEC_USE;       /* This with free the file if necessary. */
#else
        __STDIO_STREAM_FREE_FILE(stream);
+#ifdef __STDIO_HAS_OPENLIST
+{struct __STDIO_FILE_STRUCT *ptr = _stdio_openlist;
+if (ptr == stream) {
+ _stdio_openlist = stream->__nextopen;
+} else {
+ while (ptr) {
+  if (ptr->__nextopen == stream) {
+   ptr->__nextopen = stream->__nextopen;
+   break;
+  }
+  ptr = ptr->__nextopen;
+ }
+}
+}
+#endif
#endif

With the above change testcase no longer hangs.

Please fix this. Or maybe at least respond to this email.
This is my third attempt to draw attention to this problem.

Tested on today's svn. .config is attached.
--
vda
-------------- next part --------------
#
# Automatically generated make config: don't edit
# Sun Feb  4 18:24:37 2007
#
# TARGET_alpha is not set
# TARGET_arm is not set
# TARGET_bfin is not set
# TARGET_cris is not set
# TARGET_e1 is not set
# TARGET_frv is not set
# TARGET_h8300 is not set
# TARGET_hppa is not set
TARGET_i386=y
# TARGET_i960 is not set
# TARGET_ia64 is not set
# TARGET_m68k is not set
# TARGET_microblaze is not set
# TARGET_mips is not set
# TARGET_nios is not set
# TARGET_nios2 is not set
# TARGET_powerpc is not set
# TARGET_sh is not set
# TARGET_sh64 is not set
# TARGET_sparc is not set
# TARGET_v850 is not set
# TARGET_vax is not set
# TARGET_x86_64 is not set

#
# Target Architecture Features and Options
#
TARGET_ARCH="i386"
FORCE_OPTIONS_FOR_ARCH=y
# CONFIG_GENERIC_386 is not set
# CONFIG_386 is not set
CONFIG_486=y
# CONFIG_586 is not set
# CONFIG_586MMX is not set
# CONFIG_686 is not set
# CONFIG_PENTIUMII is not set
# CONFIG_PENTIUMIII is not set
# CONFIG_PENTIUM4 is not set
# CONFIG_K6 is not set
# CONFIG_K7 is not set
# CONFIG_ELAN is not set
# CONFIG_CRUSOE is not set
# CONFIG_WINCHIPC6 is not set
# CONFIG_WINCHIP2 is not set
# CONFIG_CYRIXIII is not set
# CONFIG_NEHEMIAH is not set

#
# Using ELF file format
#
ARCH_LITTLE_ENDIAN=y

#
# Using Little Endian
#
ARCH_HAS_MMU=y
ARCH_USE_MMU=y
UCLIBC_HAS_FLOATS=y
UCLIBC_HAS_FPU=y
DO_C99_MATH=y
KERNEL_HEADERS="/usr/srcdevel/uclibc/include_2.6.18.1/include"
HAVE_DOT_CONFIG=y

#
# General Library Settings
#
# HAVE_NO_PIC is not set
# DOPIC is not set
# HAVE_NO_SHARED is not set
# ARCH_HAS_NO_LDSO is not set
# HAVE_SHARED is not set
UCLIBC_CTOR_DTOR=y
# HAS_NO_THREADS is not set
# UCLIBC_HAS_THREADS is not set
UCLIBC_HAS_LFS=y
# MALLOC is not set
# MALLOC_SIMPLE is not set
MALLOC_STANDARD=y
# MALLOC_GLIBC_COMPAT is not set
UCLIBC_DYNAMIC_ATEXIT=y
# COMPAT_ATEXIT is not set
# UCLIBC_SUSV3_LEGACY is not set
# UCLIBC_SUSV3_LEGACY_MACROS is not set
UCLIBC_HAS_SHADOW=y
# UCLIBC_HAS_PROGRAM_INVOCATION_NAME is not set
UCLIBC_HAS___PROGNAME=y
UNIX98PTY_ONLY=y
ASSUME_DEVPTS=y
UCLIBC_HAS_TM_EXTENSIONS=y
UCLIBC_HAS_TZ_CACHING=y
UCLIBC_HAS_TZ_FILE=y
UCLIBC_HAS_TZ_FILE_READ_MANY=y
UCLIBC_TZ_FILE_PATH="/etc/TZ"

#
# Networking Support
#
UCLIBC_HAS_IPV6=y
UCLIBC_HAS_RPC=y
UCLIBC_HAS_FULL_RPC=y
UCLIBC_HAS_REENTRANT_RPC=y
# UCLIBC_USE_NETLINK is not set

#
# String and Stdio Support
#
UCLIBC_HAS_STRING_GENERIC_OPT=y
UCLIBC_HAS_STRING_ARCH_OPT=y
UCLIBC_HAS_CTYPE_TABLES=y
UCLIBC_HAS_CTYPE_SIGNED=y
UCLIBC_HAS_CTYPE_UNSAFE=y
# UCLIBC_HAS_CTYPE_CHECKED is not set
# UCLIBC_HAS_CTYPE_ENFORCED is not set
UCLIBC_HAS_WCHAR=y
UCLIBC_HAS_LOCALE=y
UCLIBC_PREGENERATED_LOCALE_DATA=y
# UCLIBC_DOWNLOAD_PREGENERATED_LOCALE_DATA is not set
# UCLIBC_HAS_XLOCALE is not set
# UCLIBC_HAS_HEXADECIMAL_FLOATS is not set
# UCLIBC_HAS_GLIBC_DIGIT_GROUPING is not set
# UCLIBC_HAS_GLIBC_CUSTOM_PRINTF is not set
UCLIBC_PRINTF_SCANF_POSITIONAL_ARGS=9
# UCLIBC_HAS_SCANF_GLIBC_A_FLAG is not set
# UCLIBC_HAS_STDIO_BUFSIZ_NONE is not set
# UCLIBC_HAS_STDIO_BUFSIZ_256 is not set
# UCLIBC_HAS_STDIO_BUFSIZ_512 is not set
# UCLIBC_HAS_STDIO_BUFSIZ_1024 is not set
# UCLIBC_HAS_STDIO_BUFSIZ_2048 is not set
UCLIBC_HAS_STDIO_BUFSIZ_4096=y
# UCLIBC_HAS_STDIO_BUFSIZ_8192 is not set
UCLIBC_HAS_STDIO_BUILTIN_BUFFER_NONE=y
# UCLIBC_HAS_STDIO_BUILTIN_BUFFER_4 is not set
# UCLIBC_HAS_STDIO_BUILTIN_BUFFER_8 is not set
# UCLIBC_HAS_STDIO_SHUTDOWN_ON_ABORT is not set
UCLIBC_HAS_STDIO_GETC_MACRO=y
UCLIBC_HAS_STDIO_PUTC_MACRO=y
UCLIBC_HAS_STDIO_AUTO_RW_TRANSITION=y
# UCLIBC_HAS_FOPEN_LARGEFILE_MODE is not set
# UCLIBC_HAS_FOPEN_EXCLUSIVE_MODE is not set
# UCLIBC_HAS_GLIBC_CUSTOM_STREAMS is not set
UCLIBC_HAS_PRINTF_M_SPEC=y
UCLIBC_HAS_ERRNO_MESSAGES=y
# UCLIBC_HAS_SYS_ERRLIST is not set
UCLIBC_HAS_SIGNUM_MESSAGES=y
# UCLIBC_HAS_SYS_SIGLIST is not set
UCLIBC_HAS_GNU_GETOPT=y
UCLIBC_HAS_GNU_GETSUBOPT=y

#
# Big and Tall
#
UCLIBC_HAS_REGEX=y
UCLIBC_HAS_REGEX_OLD=y
UCLIBC_HAS_FNMATCH=y
UCLIBC_HAS_FNMATCH_OLD=y
UCLIBC_HAS_WORDEXP=y
UCLIBC_HAS_FTW=y
UCLIBC_HAS_GLOB=y
# UCLIBC_HAS_GNU_GLOB is not set

#
# Library Installation Options
#
RUNTIME_PREFIX="/usr/app/uclibc-NEW/$(TARGET_ARCH)/"
DEVEL_PREFIX="/usr/app/uclibc-NEW/$(TARGET_ARCH)/usr/"

#
# Security options
#
# UCLIBC_HAS_ARC4RANDOM is not set
# HAVE_NO_SSP is not set
# UCLIBC_HAS_SSP is not set
UCLIBC_BUILD_NOEXECSTACK=y

#
# uClibc development/debugging options
#
CROSS_COMPILER_PREFIX=""
# DODEBUG is not set
DOSTRIP=y
# DOASSERTS is not set
# UCLIBC_MALLOC_DEBUGGING is not set
WARNINGS="-Wall"
# EXTRA_WARNINGS is not set
# DOMULTI is not set
# UCLIBC_MJN3_ONLY is not set


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