uclibc stdio bugs?

Sat Jan 20 14:28:18 UTC 2007

Hi Mike,

This is my second uclibc bug report, first one was also
about stdio (Subject: "gethostbyname("127.0.0.1") & stdio don't mix")
with smallish testcase, with bug pretty match narrowed down,
and I got not reply. Was it lost in the noise?

On with current bug report.

I decided to finally build fully 64bit busybox (my first 64bit
userland app for amd64 cpu).

Using uclibc svn, rev 17396 (latest).

busybox' ls.c has trouble writing to fully buffered stdout.
This was explicitly enabled recently:

int ls_main(int argc, char **argv)
{
        setvbuf(stdout, bb_common_bufsiz1, _IOFBF, BUFSIZ);

but even without this line, stdout is fully buffered if one
does e.g. "ls -l | cat".

Bug triggers only with "ls -l", here:

#if ENABLE_FEATURE_LS_USERNAME
                        printf("%-8.8s %-8.8s",
                                 get_cached_username(dn->dstat.st_uid),
                                 get_cached_groupname(dn->dstat.st_gid));
                        column += 17;
                        break;
#endif

We want to print username & groupname. get_cached_username eventually
arrives here:

int GETXXKEY_R_FUNC(GETXXKEY_R_KEYTYPE key,
                                GETXXKEY_R_ENTTYPE *__restrict resultbuf,
                                char *__restrict buffer, size_t buflen,
                                GETXXKEY_R_ENTTYPE **__restrict result)
{
        FILE *stream;
        int rv;

        *result = NULL;

fprintf(stderr,">fopen(%s)<", GETXXKEY_R_PATHNAME);
        stream = fopen(GETXXKEY_R_PATHNAME, "r");
fprintf(stderr,">fopen done<");
        if (!stream)
                return errno;
        while (1) {
                rv = ENOENT;//bb__pgsreader(GETXXKEY_R_PARSER, resultbuf, buffer, buflen, stream);
                if (!rv) {
                        if (GETXXKEY_R_TEST(resultbuf)) { /* Found key? */
                                *result = resultbuf;
                                break;
                        }
                } else {
                        if (rv == ENOENT) {     /* end-of-file encountered. */
                                rv = 0;
                        }
                        break;
                }
        }
        fclose(stream);
fprintf(stderr,">fclose done<");

        return rv;
}

GETXXKEY_R_PATHNAME == "/etc/passwd" here.

As shown above, I added debug prints. They do appear, but later ls segfaults.
Note "rv = ENOENT;//bb__pgsreader..." -- I disabled actual I/O from opened
stream. It just gets opened and closed, nothing more.

If I replace "stream = fopen...." with "stream = NULL;", ls -l no longer segfaults.
With a little bit more contrived testing, I found out that if I trigger this fopen()
just once, "ls -l" doesn't segfault, but twice or more is fatal.

Summary:
1) Have your stdout fully buffered (explicitly or implicitly)
2) do some printf's to stdout, and in the middle of that do fopen()/fclose()
   on /etc/passwd, /etc/group a few times (with no i/o in between) => segfault
   (probably on exit)

uclibc & bbox .config are attached.
--
vda
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#
# Automatically generated make config: don't edit
# Sat Jan 20 02:02:40 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 is not set
# 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=y

#
# Target Architecture Features and Options
#
TARGET_ARCH="x86_64"
FORCE_OPTIONS_FOR_ARCH=y

#
# 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"
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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