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Re: [lvm-devel] [PATCH] dmeventd coredump fix



Dne 14.1.2010 09:54, Zdenek Kabelac napsal(a):
> Hi
> 
> I've noticed that on my test machine dmeventd generates quite often weird
> coredumps with somewhat strange backtraces.
> 
> Thus I've searched for the reason and with valgrind trace I've noticed
> problem with  struct cmdline_context _cmdline
> 
> Thread 2:
> Conditional jump or move depends on uninitialised value(s)
>    at 0x4C9B826: free (vg_replace_malloc.c:325)
>    by 0x751C86F: lvm_fin (lvmcmdline.c:1213)
>    by 0x7537ACC: lvm2_exit (lvmcmdlib.c:116)
>    by 0x7365BEE: unregister_device (dmeventd_mirror.c:316)
>    by 0x804AAFE: _monitor_unregister (dmeventd.c:664)
>    by 0x804B853: _monitor_thread (dmeventd.c:805)
>    by 0x4CBC584: start_thread (pthread_create.c:300)
>    by 0x6EA426D: clone (clone.S:130)
> 
> Invalid free() / delete / delete[]
>    at 0x4C9B866: free (vg_replace_malloc.c:325)
>    by 0x751C86F: lvm_fin (lvmcmdline.c:1213)
>    by 0x7537ACC: lvm2_exit (lvmcmdlib.c:116)
>    by 0x7365BEE: unregister_device (dmeventd_mirror.c:316)
>    by 0x804AAFE: _monitor_unregister (dmeventd.c:664)
>    by 0x804B853: _monitor_thread (dmeventd.c:805)
>    by 0x4CBC584: start_thread (pthread_create.c:300)
>    by 0x6EA426D: clone (clone.S:130)
> Address 0x51 is not stack'd, malloc'd or (recently) free'd
> 
> Crash seems to appear when mirror device is reregistered during our test suit.
> Not really sure if it's related to some other reported problems.
> 
> Basically we need to clear commands_size & num_commands and
> it doesn't matter if it is in init or finish -
> 
> I'm proposing this oneline patch:
> 
> --- tools/lvmcmdline.c	11 Jan 2010 19:19:17 -0000	1.111
> +++ tools/lvmcmdline.c	14 Jan 2010 08:33:50 -0000
>  -1192,6 +1192,7 @@ struct cmd_context *init_lvm(void)
>  {
>  	struct cmd_context *cmd;
> 
> +	memset(&_cmdline, 0, sizeof(_cmdline));
>  	_cmdline.the_args = &_the_args[0];
> 
>  	if (!(cmd = create_toolcontext(0, NULL)))
> 

Ok - patch above has some problems with order of calling lvm2_init() calls;

So here comes simpler version which only clears structure elements right after
they are being released:

--- tools/lvmcmdline.c	11 Jan 2010 19:19:17 -0000	1.111
+++ tools/lvmcmdline.c	15 Jan 2010 12:51:58 -0000
@@ -1213,6 +1213,10 @@ static void _fin_commands(void)
 		dm_free(_cmdline.commands[i].valid_args);

 	dm_free(_cmdline.commands);
+
+	_cmdline.commands = NULL;
+	_cmdline.num_commands = 0;
+	_cmdline.commands_size = 0;
 }

 void lvm_fin(struct cmd_context *cmd)


Zdenek


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