linux-kernel - netfilter: BUG: sleeping function called from invalid context

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Message-ID: <20090610161935.0f8b1949@osiris.boeblingen.de.ibm.com>
Date:	Wed, 10 Jun 2009 16:19:35 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Eric Leblond <eric@....fr>, Patrick McHardy <kaber@...sh.net>
Cc:	Maran Pakkirisamy <maranpsamy@...ibm.com>,
	Andreas Krebbel <krebbel1@...ibm.com>,
	<linux-kernel@...r.kernel.org>, netfilter-devel@...r.kernel.org
Subject: netfilter: BUG: sleeping function called from invalid context

Hi,

Maran reported the bug below (vanilla 2.6.30-rc8):

BUG: sleeping function called from invalid context at /mnt/s390test/linux-2.6-tip/arch/s390/include/asm/uaccess.h:234 
in_atomic(): 1, irqs_disabled(): 0, pid: 3245, name: sysctl 
CPU: 1 Not tainted 2.6.30-rc8-tipjun10-02053-g39ae214 #1 
Process sysctl (pid: 3245, task: 000000007f675da0, ksp: 000000007eb17cf0) 
0000000000000000 000000007eb17be8 0000000000000002 0000000000000000  
       000000007eb17c88 000000007eb17c00 000000007eb17c00 0000000000048156  
       00000000003e2de8 000000007f676118 000000007eb17f10 0000000000000000  
       0000000000000000 000000007eb17be8 000000000000000d 000000007eb17c58  
       00000000003e2050 000000000001635c 000000007eb17be8 000000007eb17c30  
Call Trace: 
(Ý<00000000000162e6>¨ show_trace+0x13a/0x148) 
 Ý<00000000000349ea>¨ __might_sleep+0x13a/0x164 
 Ý<0000000000050300>¨ proc_dostring+0x134/0x22c 
 Ý<0000000000312b70>¨ nf_log_proc_dostring+0xfc/0x188 
 Ý<0000000000136f5e>¨ proc_sys_call_handler+0xf6/0x118 
 Ý<0000000000136fda>¨ proc_sys_read+0x26/0x34 
 Ý<00000000000d6e9c>¨ vfs_read+0xac/0x158 
 Ý<00000000000d703e>¨ SyS_read+0x56/0x88 
 Ý<0000000000027f42>¨ sysc_noemu+0x10/0x16 

The code that introduces the bug came in with 17625274 "netfilter:
sysctl support of logger choice".

There we have this chunk:

+               rcu_read_lock();
+               logger = rcu_dereference(nf_loggers[tindex]);
+               if (!logger)
+                       table->data = "NONE";
+               else
+                       table->data = logger->name;
+               r = proc_dostring(table, write, filp, buffer, lenp, ppos);
+               rcu_read_unlock();

proc_dostring() will call copy_from_user() while preemption is disabled
because of rcu_read_lock().
Looks like somebody needs to fix this ;)
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