[Bug libc/12091] New: gconv: Allow iconv_open to recurse

[Bug libc/12091] New: gconv: Allow iconv_open to recurse

[dtrebbien at gmail dot com]

I am working on a gconv module in which I would like to be able to call `iconv_open` within the 
module's `gconv_init` function. It is particularly important that my module be able to call `iconv_open` 
within `gconv_init` because only `gconv_init` can return an appropriate error code should 
`iconv_open` fail;  however, the way that glibc `iconv_open` is currently programmed, calling 
`iconv_open` within `gconv_init` causes deadlock due to the fact that the current thread attempts to 
lock the non-reentrant mutex `__gconv_lock` a second time:

$ gdb iconv
GNU gdb (GDB) 7.2-debian
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/iconv...Reading symbols from /usr/lib/debug/usr/bin/iconv...done.
done.
(gdb) break gconv_init
Function "gconv_init" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y

Breakpoint 1 (gconv_init) pending.
(gdb) run -f UTF-8 -t ABC TEST.txt
Starting program: /usr/bin/iconv -f UTF-8 -t ABC TEST.txt

Breakpoint 1, gconv_init (step=0x8056840) at ABC.c:8
8	  iconv_t cd = iconv_open("UTF-8", "ISO-8859-1");
(gdb) s
iconv_open (tocode=0xb7fd75df <error reading variable>, 
    fromcode=0xb7fd75d4 <error reading variable>) at iconv_open.c:34
34	iconv_open.c: No such file or directory.
	in iconv_open.c
(gdb) finish
Run till exit from #0  iconv_open (tocode=0xb7fd75df <error reading variable>, 
    fromcode=0xb7fd75d4 <error reading variable>) at iconv_open.c:34
^C
Program received signal SIGINT, Interrupt.
0xb7fe2416 in __kernel_vsyscall ()
(gdb) bt
#0  0xb7fe2416 in __kernel_vsyscall ()
#1  0xb7f64163 in __lll_lock_wait_private ()
    at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:95
#2  0xb7ea452b in _L_lock_2093 () at gconv_db.c:761
#3  0xb7ea433c in __gconv_find_transform (
    toset=0xbffff1c0 <error reading variable>, 
    fromset=0xbffff1a0 <error reading variable>, handle=<value optimized out>, 
    nsteps=0xbffff180, flags=0) at gconv_db.c:728
#4  0xb7ea2c7a in __gconv_open (toset=<value optimized out>, 
    fromset=<value optimized out>, handle=<value optimized out>, flags=0)
    at gconv_open.c:174
#5  0xb7ea287c in iconv_open (tocode=0xb7fd75df <error reading variable>, 
    fromcode=0xb7fd75d4 <error reading variable>) at iconv_open.c:72
#6  0xb7fd7526 in gconv_init (step=0x8056840) at ABC.c:8
#7  0xb7eaaf1e in find_module (directory=<value optimized out>, 
    filename=<value optimized out>, result=0x8056840) at gconv_cache.c:217
#8  0xb7eab210 in __gconv_lookup_cache (toset=<value optimized out>, 
    fromset=<value optimized out>, handle=<value optimized out>, 
    nsteps=0xbffff334, flags=<value optimized out>) at gconv_cache.c:340
#9  0xb7ea4355 in __gconv_find_transform (
    toset=0xbffff370 <error reading variable>, 
    fromset=0xbffff360 <error reading variable>, handle=<value optimized out>, 
    nsteps=0xbffff334, flags=0) at gconv_db.c:730
---Type <return> to continue, or q <return> to quit---
#10 0xb7ea2c7a in __gconv_open (toset=<value optimized out>, 
    fromset=<value optimized out>, handle=<value optimized out>, flags=0)
    at gconv_open.c:174
#11 0xb7ea287c in iconv_open (tocode=0xbffff683 <error reading variable>, 
    fromcode=0xbffff67a <error reading variable>) at iconv_open.c:72
#12 0x0804a428 in main (argc=6, argv=0xbffff4f4) at iconv_prog.c:210
(gdb) 


Note: The problematic locking occurs within `__gconv_find_transform`.

-- 
           Summary: gconv: Allow iconv_open to recurse
           Product: glibc
           Version: 2.11
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: libc
        AssignedTo: drepper dot fsp at gmail dot com
        ReportedBy: dtrebbien at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=12091

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[Bug libc/12091] gconv: Allow iconv_open to recurse

[dtrebbien at gmail dot com]

------- Additional Comments From dtrebbien at gmail dot com  2010-10-03 17:51 -------
Created an attachment (id=5031)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=5031&action=view)
Test case

This is the test case that I used with the GDB session that is listed in the
description. To use:
tar jxvf bug-12091.tar.bz2 && cd bug-12091 && make && sudo make install

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http://sourceware.org/bugzilla/show_bug.cgi?id=12091

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[Bug libc/12091] gconv: Allow iconv_open to recurse

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=12091

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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[Bug libc/12091] gconv: Allow iconv_open to recurse

[schwab@linux-m68k.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12091

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|drepper.fsp at gmail dot    |unassigned at sourceware
                   |com                         |dot org

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