netfilter: BUG: sleeping function called from invalid context

Heiko Carstens
2009-06-10T14:20:01Z

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 ;)