Re: SIGSEGV, Segmentation fault.

[Igor Homyakov]

What about using string safe library (like Vstr or FireString) ?
i think Vstr is beter.


* Jan-Henrik Haukeland <hauk @ tildeslash . com> [030521 02:17]:
> I'm not sure and I may be wrong, but from the top of my head I do not think
> this is a buffer-size problem i.e. it's not necessary to add 1 byte to the
> buffer when snprintf is used. The buffer is not going to get overrun and
> snprintf adds a '\0' char at the end of the buffer. The man page for *printf
> says:

>    sprintf  stores the output in the specified char array str
>    and snprintf limits number of characters written to str to
>    at  most  size (including terminating 0)...

> And as you can see in the strange string Igor got when he ran gdb,  the NUL
> char was added, the rest of the garble is normal (probably) since the string
> was uninitialized. It seems that the problem is vsnprintf and it fails (with
> malloc!?) because it has problems with the format string? Again from the man
> page:

>   For sprintf and snprintf, the behavior is also  undefined  if  the  output
>   *<[str>>  overlaps with one of the arguments.

> Undefined behaviour usually means SIGSEGV :-) So my two cents are on the
> vsnprintf statement and on the format argument. (I'm on windows right now and
> helping my brother building a house in another town so I cannot check the 
> patch
> right now, but I'll be back next week).

> Cheers!

> Jan-Henrik

> > -----Original Message-----
> > From: address@hidden
> > [mailto:address@hidden
> > Behalf Of Martin Pala
> > Sent: 20. mai 2003 21:45
> > To: This is the general mailing list for monit
> > Subject: Re: SIGSEGV, Segmentation fault.
> >
> >
> > This kind of error (i think it was the cause of problem) was in the
> > sources more then once - new patch which should generaly fix it
> > attached, please try it, Igor.
> >
> > Thanks,
> > Martin
> >
> > Martin wrote:
> >
> > >Hi Igor,
> > >
> > >can you try attached patch?
> > >
> > >Thanks,
> > >
> > >Cheers,
> > >Martin
> > >
> > >----- P?vodn? zpr?va -----
> > >Od: Igor Homyakov <address@hidden>
> > >Datum: ?ter?, 20. kv?tna 2003 v 9:32 dop.
> > >P?edm?t: SIGSEGV, Segmentation fault.
> > >
> > >
> > >
> > >>address@hidden monit-3.2]# gdb ./monit
> > >>GNU gdb ALT Linux (5.2.1-alt2)
> > >>Copyright 2002 Free Software Foundation, Inc.
> > >>GDB is free software, covered by the GNU
> > >>General Public License, and you are
> > >>welcome to change it and/or distribute copies
> > >>of it under certain conditions.
> > >>Type "show copying" to see the conditions.
> > >>There is absolutely no warranty for GDB.
> > >>Type "show warranty" for details.
> > >>This GDB was configured as "i586-alt-linux"...
> > >>(gdb) break do_default
> > >>Breakpoint 1 at 0x804f09c: file monitor.c,
> > >>line 496.
> > >>(gdb) run
> > >>Starting program:
> > >>/home/homyakov/RPM/BUILD/monit-3.2/monit
> > >>[New Thread 1024 (LWP 14649)]
> > >>[Switching to Thread 1024 (LWP 14649)]
> > >>
> > >>Breakpoint 1, do_default () at monitor.c:496
> > >>496       if(Run.isdaemon) {
> > >>(gdb) n
> > >>498         if(do_wakeupcall()) {
> > >>(gdb) n
> > >>504         log("Starting %s daemon\n", prog);
> > >>(gdb) s
> > >>log (format=0x80619e0 "Starting %s daemon\n")
> > >>at log.c:116
> > >>116       ASSERT(format);
> > >>(gdb) s
> > >>118       va_start(ap,format);
> > >>(gdb) n
> > >>119       vsnprintf(msg, STRLEN, format, ap);
> > >>(gdb) n
> > >>122       if(! Run.dolog) goto nolog;
> > >>(gdb) n
> > >>124       if(Run.use_syslog) {
> > >>(gdb) n
> > >>126         syslog(LOG_ERR|LOG_USER, "%s", msg);
> > >>(gdb) print msg
> > >>$1 = "Starting monit
> > >>
> > >>
> > >>
> > >daemon\n\0*???\177t?\004\bH5\a\b\220??\177\210??\177;?\004\b/var/run
> > /mon\0\0\0\0id\0*???*x??*0??*???*???*\e\0?*?\232?*\220R?*\200N?*???\1
> > 77\216??*\235\035?*???*x??*0??*\0\0\0\0???*\0\0\0\00??*0??\177?D?*\e\
> > address@hidden(??\177uC\005\bH5\a\b\0\0\0\0(??\177L\214?
> > *L\214?*`\234?*"...(gdb)
> > >n
> > >
> > >
> > >>
> > >>Program received signal SIGSEGV, Segmentation
> > >>fault.0x2ac6011a in malloc () from
> > >>/lib/libc.so.6(gdb) where
> > >>#0  0x2ac6011a in malloc () from /lib/libc.so.6
> > >>#1  0x2ac5fc7e in malloc () from /lib/libc.so.6
> > >>#2  0x2ac57997 in open_memstream () from
> > >>/lib/libc.so.6#3  0x2acb90a9 in vsyslog ()
> > >>from /lib/libc.so.6
> > >>#4  0x2acb8ebd in syslog () from /lib/libc.so.6
> > >>#5  0x0804d4f5 in log (format=0x80619e0
> > >>"Starting %s daemon\n") at log.c:126
> > >>#6  0x0804f0cf in do_default () at monitor.c:504
> > >>#7  0x0804ec5d in do_action (args=0x7ffff8f4)
> > >>at monitor.c:316
> > >>#8  0x0804e917 in main (argc=1,
> > >>argv=0x7ffff8f4) at monitor.c:96
> > >>#9  0x2ac0b652 in __libc_start_main () from
> > >>/lib/libc.so.6
> > >>
> > >>--
> > >>Igor Homyakov
> > >><homyakov AT ramax.spb.ru>
> > >>
> > >>
> > >>--
> > >>To unsubscribe:
> > >>http://mail.nongnu.org/mailman/listinfo/monit-
> > >>general
> > >>
> >
> >



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-- 
Igor Homyakov
<homyakov AT ramax.spb.ru>