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Bug#279722: libc6: application sometimes crashes, valgrind shows error in gconv_db.c


 This is a followup for Debian bug <http://bugs.debian.org/279722>.

wim delvaux <wim.delvaux@adaptiveplanet.com> - Thu, Nov 04, 2004:

> Valgrind shows the following backtrace ...
> ==7105== Invalid read of size 4
> ==7105==    at 0x1C22857E: __gconv_release_step (gconv_db.c:198)
> ==7105==    by 0x1C22914C: __gconv_close_transform (gconv_db.c:751)

 I can get that one fairly easily with:
    % valgrind --db-attach=yes ls -l

 (% locale LANG=fr_FR@euro LC_CTYPE=fr_FR@euro LC_NUMERIC=fr_FR@euro
 LC_TIME=fr_FR@euro LC_COLLATE=fr_FR@euro LC_MONETARY=fr_FR@euro
 LC_MESSAGES=fr_FR@euro LC_PAPER=fr_FR@euro LC_NAME=fr_FR@euro

 I get the same bt, I installed the -dbg version of glibc and debuilded
 a part of the source (to get the patches applied):

(gdb) bt
#0  0x1b94e58f in __gconv_release_step (step=0x1bae2ccc) at gconv_db.c:198
#1  0x1b94f14d in __gconv_close_transform (steps=0x1bae2c90, nsteps=2)
    at gconv_db.c:751
#2  0x1b94e256 in __gconv_close (cd=0x1bae3868) at gconv_close.c:64
#3  0x1b95c54d in _nl_free_domain_conv (domain=0x1baba698) at loadmsgcat.c:873
#4  0x1b95d0b4 in _nl_unload_domain (domain=0x1baba698) at loadmsgcat.c:1289
#5  0x1ba42afd in free_mem () at finddomain.c:179
#6  0x1ba42c45 in *__GI___libc_freeres () at set-freeres.c:49
#7  0x1b8fec51 in _vgw__freeres () at vg_intercept.c:117
#8  0x1b962b18 in *__GI_exit (status=0) at exit.c:82

 I think the problem is in iconv/gconv_close.c, in __gconv_close() at
 the very end of the file:
  while (!((drunp++)->__flags & __GCONV_IS_LAST));

  /* Free the data allocated for the descriptor.  */
  free (cd);

  /* Close the participating modules.  */
  return __gconv_close_transform (srunp, nsteps);

 I think "srunp" uses a reference in "cd".

 I already tried in the past to build glibc on my system, and this was
 too long a task for my laptop, could someone try swapping the free
 after the __gconv_close_transform() or hand me a build if he can't
 reproduce the bug?


Loïc Minier <lool@dooz.org>
"Neutral President: I have no strong feelings one way or the other."

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