Patchwork 3.11-rc7:BUG: soft lockup

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Submitter dingtianhong
Date Sept. 2, 2013, 7:44 a.m.
Message ID <522441E9.8040809@huawei.com>
Download mbox | patch
Permalink /patch/271698/
State RFC
Delegated to: David Miller
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Comments

dingtianhong - Sept. 2, 2013, 7:44 a.m.
On 2013/9/2 14:06, Baoquan He wrote:
> Hi both,
> 
> Thanks for your patches. I tried to test your patches,  first the 2nd 
> one, namely Hillf's patch, it's OK. Then when I wanted to reproduce and 
> test Cong's patch, it failed to happen again. 
> 
> I remember this bug happened randomly at the very beginning, 
> just after kernel compiling  it always happened one day. 
> 
> So maybe when it happened again, I will test your patch separately. 
> 
> Baoquan
> Thanks 
> 
> On 08/31/2013 11:25 AM, Hillf Danton wrote:
>> On Fri, Aug 30, 2013 at 8:18 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>>> Cc'ing netdev
>>>
>>> On Fri, Aug 30, 2013 at 4:20 PM, Baoquan He <baoquan.he@gmail.com> wrote:
>>>> Hi,
>>>>
>>>> I tried the 3.11.0-rc7+ on x86_64, and after bootup, the soft lockup bug
>>>> happened.
>>>>
>>>> [   48.895000] BUG: soft lockup - CPU#1 stuck for 22s! [ebtables:444]
>>>> [   48.901191] Modules linked in: bnep(F) bluetooth(F) ebtables(F)
>>>> ip6table_filter(F) ip6_tables(F) rfkill(F) snd_hda_intel(F+)
>>>> snd_hda_codec(F) snd_hwdep(F) snd_seq(F) sn)
>>>> [   48.950034] CPU: 1 PID: 444 Comm: ebtables Tainted: GF     D
>>>> 3.11.0-rc7+ #1
>>>> [   48.957433] Hardware name: Hewlett-Packard HP Z420 Workstation/1589,
>>>> BIOS J61 v01.02 03/09/2012
>>>> [   48.966131] task: ffff88040c2dc650 ti: ffff8804187d2000 task.ti:
>>>> ffff8804187d2000
>>>> [   48.973610] RIP: 0010:[<ffffffff812e57a7>]  [<ffffffff812e57a7>]
>>>> strcmp+0x27/0x40
>>>> [   48.981119] RSP: 0018:ffff8804187d3db8  EFLAGS: 00000246
>>>> [   48.986430] RAX: 0000000000000000 RBX: 00007fffda942730 RCX:
>>>> ffff8804187d3fd8
>>>> [   48.993566] RDX: 0000000000000000 RSI: ffff8804187d3e01 RDI:
>>>> ffffffff81cb8a39
>>>> [   49.000707] RBP: ffff8804187d3db8 R08: 00000000fffffff2 R09:
>>>> 0000000000000000
>>>> [   49.007841] R10: 0000000000000163 R11: 0000000000000000 R12:
>>>> ffffffff8128300c
>>>> [   49.014972] R13: ffff8804187d3d98 R14: ffff8804187d3ef4 R15:
>>>> 0000000000000004
>>>> [   49.022112] FS:  00007faab6589740(0000) GS:ffff88042fc80000(0000)
>>>> knlGS:0000000000000000
>>>> [   49.030194] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [   49.035942] CR2: 0000003f0d810414 CR3: 000000040d2cc000 CR4:
>>>> 00000000000407e0
>>>> [   49.043077] Stack:
>>>> [   49.045096]  ffff8804187d3de8 ffffffffa0249674 0000000000000080
>>>> ffffffff81cb8180
>>>> [   49.052559]  00007fffda942730 ffff8804187d3ef4 ffff8804187d3ea0
>>>> ffffffffa02497a9
>>>> [   49.060020]  0000000000000000 00007265746c6966 0000003f0d7b92c0
>>>> 00007fffda942850
>>>> [   49.067487] Call Trace:
>>>> [   49.069949]  [<ffffffffa0249674>]
>>>> find_inlist_lock.constprop.16+0x54/0x100 [ebtables]
>>>> [   49.077779]  [<ffffffffa02497a9>] do_ebt_get_ctl+0x89/0x1d0 [ebtables]
>>>> [   49.084306]  [<ffffffff81551ca8>] nf_getsockopt+0x68/0x90
>>>> [   49.089717]  [<ffffffff81560d40>] ip_getsockopt+0x80/0xa0
>>>> [   49.095113]  [<ffffffff815835c5>] raw_getsockopt+0x25/0x50
>>>> [   49.100588]  [<ffffffff8150ddd4>] sock_common_getsockopt+0x14/0x20
>>>> [   49.106766]  [<ffffffff8150d208>] SyS_getsockopt+0x68/0xd0
>>>> [   49.112257]  [<ffffffff8162c682>] system_call_fastpath+0x16/0x1b
>>>> [   49.118260] Code: 00 00 00 00 55 48 89 e5 eb 0e 66 2e 0f 1f 84 00 00
>>>> 00 00 00 84 c0 74 1c 48 83 c7 01 0f b6 47 ff 48 83 c6 01 3a 46 ff 74 eb
>>>> 19 c0 <83> c8 01 5d c3 0f 1
>>>> [   76.925880] BUG: soft lockup - CPU#1 stuck for 22s! [ebtables:444]
>>>> [   76.932069] Modules linked in: bnep(F) bluetooth(F) ebtables(F)
>>>> ip6table_filter(F) ip6_tables(F) rfkill(F) snd_hda_intel(F+)
>>>> snd_hda_codec(F) snd_hwdep(F) snd_seq(F) sn)
>>>> [   76.980847] CPU: 1 PID: 444 Comm: ebtables Tainted: GF     D
>>>> 3.11.0-rc7+ #1
>>>> [   76.988245] Hardware name: Hewlett-Packard HP Z420 Workstation/1589,
>>>> BIOS J61 v01.02 03/09/2012
>>>> [   76.996940] task: ffff88040c2dc650 ti: ffff8804187d2000 task.ti:
>>>> ffff8804187d2000
>>>> [   77.004426] RIP: 0010:[<ffffffff812e5784>]  [<ffffffff812e5784>]
>>>> strcmp+0x4/0x40
>>>> [   77.011849] RSP: 0018:ffff8804187d3db8  EFLAGS: 00000212
>>>> [   77.017163] RAX: 0000000000000001 RBX: 00007fffda942730 RCX:
>>>> ffff8804187d3fd8
>>>> [   77.024304] RDX: 0000000000000000 RSI: ffff8804187d3e00 RDI:
>>>> ffffffff81cb8a38
>>>> [   77.031434] RBP: ffff8804187d3db8 R08: 00000000fffffff2 R09:
>>>> 0000000000000000
>>>> [   77.038566] R10: 0000000000000163 R11: 0000000000000000 R12:
>>>> ffffffff8128300c
>>>> [   77.045699] R13: ffff8804187d3d98 R14: ffff8804187d3ef4 R15:
>>>> 0000000000000004
>>>> [   77.052842] FS:  00007faab6589740(0000) GS:ffff88042fc80000(0000)
>>>> knlGS:0000000000000000
>>>> [   77.060934] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [   77.066668] CR2: 0000003f0d810414 CR3: 000000040d2cc000 CR4:
>>>> 00000000000407e0
>>>> [   77.073799] Stack:
>>>> [   77.075818]  ffff8804187d3de8 ffffffffa0249674 0000000000000080
>>>> ffffffff81cb8180
>>>> [   77.083287]  00007fffda942730 ffff8804187d3ef4 ffff8804187d3ea0
>>>> ffffffffa02497a9
>>>> [   77.090749]  0000000000000000 00007265746c6966 0000003f0d7b92c0
>>>> 00007fffda942850
>>>> [   77.098215] Call Trace:
>>>> [   77.100668]  [<ffffffffa0249674>]
>>>> find_inlist_lock.constprop.16+0x54/0x100 [ebtables]
>>>> [   77.108500]  [<ffffffffa02497a9>] do_ebt_get_ctl+0x89/0x1d0 [ebtables]
>>>> [   77.115035]  [<ffffffff81551ca8>] nf_getsockopt+0x68/0x90
>>>> [   77.120438]  [<ffffffff81560d40>] ip_getsockopt+0x80/0xa0
>>>> [   77.125845]  [<ffffffff815835c5>] raw_getsockopt+0x25/0x50
>>>> [   77.131328]  [<ffffffff8150ddd4>] sock_common_getsockopt+0x14/0x20
>>>> [   77.137515]  [<ffffffff8150d208>] SyS_getsockopt+0x68/0xd0
>>>> [   77.143011]  [<ffffffff8162c682>] system_call_fastpath+0x16/0x1b
>>>> [   77.149019] Code: 0f 1f 80 00 00 00 00 48 83 c6 01 0f b6 4e ff 48 83
>>>> c2 01 84 c9 88 4a ff 75 ed 5d c3 66 66 2e 0f 1f 84 00 00 00 00 00 55 48
>>>> 89 e5 <eb> 0e 66 2e 0f 1f 8
>>>
>>> Does the following patch help?
>>>
>>>
>>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>>> index ac78024..4a0ec8f 100644
>>> --- a/net/bridge/netfilter/ebtables.c
>>> +++ b/net/bridge/netfilter/ebtables.c
>>> @@ -1503,6 +1503,10 @@ static int do_ebt_get_ctl(struct sock *sk, int
>>> cmd, void __user *user, int *len)
>>>         if (copy_from_user(&tmp, user, sizeof(tmp)))
>>>                 return -EFAULT;
>>>
>>> +       if (memscan(tmp.name, '\0', EBT_TABLE_MAXNAMELEN) ==
>>> +                   (tmp.name + EBT_TABLE_MAXNAMELEN))
>>> +               return -EINVAL;
>>> +
>>>         t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
>>>         if (!t)
>>>                 return ret;
>>> --
>>>
>> release lock!!
>>
>> --- a/net/bridge/netfilter/ebtables.c Sat Aug 31 11:12:54 2013
>> +++ b/net/bridge/netfilter/ebtables.c Sat Aug 31 11:15:24 2013
>> @@ -332,8 +332,10 @@ find_inlist_lock_noload(struct list_head
>>   return NULL;
>>
>>   list_for_each_entry(e, head, list) {
>> - if (strcmp(e->name, name) == 0)
>> + if (strcmp(e->name, name) == 0) {
>> + mutex_unlock(mutex);
>>   return e;
>> + }
>>   }
>>   *error = -ENOENT;
>>   mutex_unlock(mutex);
>> --
> 

please try this patch and give me the result, thanks.

Return the correct value if mutex_lock_interruptible() failed, avoid
confusion with that the modules is not exist, and deal with the return
value in right way.

if mutex_lock_interrupt() failed, sh

Signed-off-by: root <root@linux-yocto.site>
---
 net/bridge/netfilter/ebtables.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)
Baoquan He - Sept. 2, 2013, 8:24 a.m.
Hi Tianhong,

I applied your patch and execute below cmd. 
Then keyboard inputting problems happened, 
I can't enter user/password correctly, then reboot again, it's OK now.

The original bug still can't be reproduced.

make SUBDIRS=net/bridge/netfilter/
cp /net/bridge/netfilter/ebtables.ko
/lib/modules/3.11.0-rc7+/kernel/net/bridge/netfilter/ebtables.ko
depmod
modprobe ebtables.ko
reboot

Baoquan
Thanks

> please try this patch and give me the result, thanks.
>
> Return the correct value if mutex_lock_interruptible() failed, avoid
> confusion with that the modules is not exist, and deal with the return
> value in right way.
>
> if mutex_lock_interrupt() failed, sh
>
> Signed-off-by: root <root@linux-yocto.site>
> ---
>  net/bridge/netfilter/ebtables.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index ac78024..e7fe9f8 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -322,17 +322,14 @@ static inline void *
>  find_inlist_lock_noload(struct list_head *head, const char *name, int *error,
>     struct mutex *mutex)
>  {
> -	struct {
> -		struct list_head list;
> -		char name[EBT_FUNCTION_MAXNAMELEN];
> -	} *e;
> +	struct ebt_table *e;
>  
>  	*error = mutex_lock_interruptible(mutex);
>  	if (*error != 0)
> -		return NULL;
> +		return ERR_PTR(-EINTR);
>  
>  	list_for_each_entry(e, head, list) {
> -		if (strcmp(e->name, name) == 0)
> +		 if (strcmp(e->name, name) == 0 && try_module_get(e->me))
>  			return e;
>  	}
>  	*error = -ENOENT;
> @@ -1005,7 +1002,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
>  		goto free_counterstmp;
>  
>  	t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
> -	if (!t) {
> +	if (IS_ERR_OR_NULL(t)) {
>  		ret = -ENOENT;
>  		goto free_iterate;
>  	}
> @@ -1284,7 +1281,7 @@ static int do_update_counters(struct net *net, const char *name,
>  		return -ENOMEM;
>  
>  	t = find_table_lock(net, name, &ret, &ebt_mutex);
> -	if (!t)
> +	if (IS_ERR_OR_NULL(t))
>  		goto free_tmp;
>  
>  	if (num_counters != t->private->nentries) {
> @@ -1504,7 +1501,7 @@ static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>  		return -EFAULT;
>  
>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
> -	if (!t)
> +	if (IS_ERR_OR_NULL(t))
>  		return ret;
>  
>  	switch(cmd) {
> @@ -2319,7 +2316,7 @@ static int compat_do_ebt_get_ctl(struct sock *sk, int cmd,
>  		return -EFAULT;
>  
>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
> -	if (!t)
> +	if (IS_ERR_OR_NULL(t))
>  		return ret;
>  
>  	xt_compat_lock(NFPROTO_BRIDGE);

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dingtianhong - Sept. 2, 2013, 9:04 a.m.
On 2013/9/2 16:24, Baoquan He wrote:
> Hi Tianhong,
> 
> I applied your patch and execute below cmd. 
> Then keyboard inputting problems happened, 
> I can't enter user/password correctly, then reboot again, it's OK now.

Thanks for your work, I don't understand that the keyboard problem is the patch fault or your system problem, 
if it is not happen again, I think the problem is fixed.

> 
> The original bug still can't be reproduced.
> 
> make SUBDIRS=net/bridge/netfilter/
> cp /net/bridge/netfilter/ebtables.ko
> /lib/modules/3.11.0-rc7+/kernel/net/bridge/netfilter/ebtables.ko
> depmod
> modprobe ebtables.ko
> reboot
> 
> Baoquan
> Thanks
> 
>> please try this patch and give me the result, thanks.
>>
>> Return the correct value if mutex_lock_interruptible() failed, avoid
>> confusion with that the modules is not exist, and deal with the return
>> value in right way.
>>
>> if mutex_lock_interrupt() failed, sh
>>
>> Signed-off-by: root <root@linux-yocto.site>
>> ---
>>  net/bridge/netfilter/ebtables.c | 17 +++++++----------
>>  1 file changed, 7 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>> index ac78024..e7fe9f8 100644
>> --- a/net/bridge/netfilter/ebtables.c
>> +++ b/net/bridge/netfilter/ebtables.c
>> @@ -322,17 +322,14 @@ static inline void *
>>  find_inlist_lock_noload(struct list_head *head, const char *name, int *error,
>>     struct mutex *mutex)
>>  {
>> -	struct {
>> -		struct list_head list;
>> -		char name[EBT_FUNCTION_MAXNAMELEN];
>> -	} *e;
>> +	struct ebt_table *e;
>>  
>>  	*error = mutex_lock_interruptible(mutex);
>>  	if (*error != 0)
>> -		return NULL;
>> +		return ERR_PTR(-EINTR);
>>  
>>  	list_for_each_entry(e, head, list) {
>> -		if (strcmp(e->name, name) == 0)
>> +		 if (strcmp(e->name, name) == 0 && try_module_get(e->me))
>>  			return e;
>>  	}
>>  	*error = -ENOENT;
>> @@ -1005,7 +1002,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
>>  		goto free_counterstmp;
>>  
>>  	t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
>> -	if (!t) {
>> +	if (IS_ERR_OR_NULL(t)) {
>>  		ret = -ENOENT;
>>  		goto free_iterate;
>>  	}
>> @@ -1284,7 +1281,7 @@ static int do_update_counters(struct net *net, const char *name,
>>  		return -ENOMEM;
>>  
>>  	t = find_table_lock(net, name, &ret, &ebt_mutex);
>> -	if (!t)
>> +	if (IS_ERR_OR_NULL(t))
>>  		goto free_tmp;
>>  
>>  	if (num_counters != t->private->nentries) {
>> @@ -1504,7 +1501,7 @@ static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>>  		return -EFAULT;
>>  
>>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
>> -	if (!t)
>> +	if (IS_ERR_OR_NULL(t))
>>  		return ret;
>>  
>>  	switch(cmd) {
>> @@ -2319,7 +2316,7 @@ static int compat_do_ebt_get_ctl(struct sock *sk, int cmd,
>>  		return -EFAULT;
>>  
>>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
>> -	if (!t)
>> +	if (IS_ERR_OR_NULL(t))
>>  		return ret;
>>  
>>  	xt_compat_lock(NFPROTO_BRIDGE);
> 
> 
> .
> 


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Baoquan He - Sept. 2, 2013, 12:09 p.m.
On 09/02/2013 05:04 PM, Ding Tianhong wrote:
> On 2013/9/2 16:24, Baoquan He wrote:
>> Hi Tianhong,
>>
>> I applied your patch and execute below cmd. 
>> Then keyboard inputting problems happened, 
>> I can't enter user/password correctly, then reboot again, it's OK now.
> Thanks for your work, I don't understand that the keyboard problem is the patch fault or your system problem, 
> if it is not happen again, I think the problem is fixed.

Yeah,  I will wait and see if it will happen again. Up to now, it's OK.

Thank you all for help.

Baoquan
Thanks

>
>> The original bug still can't be reproduced.
>>
>> make SUBDIRS=net/bridge/netfilter/
>> cp /net/bridge/netfilter/ebtables.ko
>> /lib/modules/3.11.0-rc7+/kernel/net/bridge/netfilter/ebtables.ko
>> depmod
>> modprobe ebtables.ko
>> reboot
>>
>> Baoquan
>> Thanks
>>
>>> please try this patch and give me the result, thanks.
>>>
>>> Return the correct value if mutex_lock_interruptible() failed, avoid
>>> confusion with that the modules is not exist, and deal with the return
>>> value in right way.
>>>
>>> if mutex_lock_interrupt() failed, sh
>>>
>>> Signed-off-by: root <root@linux-yocto.site>
>>> ---
>>>  net/bridge/netfilter/ebtables.c | 17 +++++++----------
>>>  1 file changed, 7 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>>> index ac78024..e7fe9f8 100644
>>> --- a/net/bridge/netfilter/ebtables.c
>>> +++ b/net/bridge/netfilter/ebtables.c
>>> @@ -322,17 +322,14 @@ static inline void *
>>>  find_inlist_lock_noload(struct list_head *head, const char *name, int *error,
>>>     struct mutex *mutex)
>>>  {
>>> -	struct {
>>> -		struct list_head list;
>>> -		char name[EBT_FUNCTION_MAXNAMELEN];
>>> -	} *e;
>>> +	struct ebt_table *e;
>>>  
>>>  	*error = mutex_lock_interruptible(mutex);
>>>  	if (*error != 0)
>>> -		return NULL;
>>> +		return ERR_PTR(-EINTR);
>>>  
>>>  	list_for_each_entry(e, head, list) {
>>> -		if (strcmp(e->name, name) == 0)
>>> +		 if (strcmp(e->name, name) == 0 && try_module_get(e->me))
>>>  			return e;
>>>  	}
>>>  	*error = -ENOENT;
>>> @@ -1005,7 +1002,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
>>>  		goto free_counterstmp;
>>>  
>>>  	t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
>>> -	if (!t) {
>>> +	if (IS_ERR_OR_NULL(t)) {
>>>  		ret = -ENOENT;
>>>  		goto free_iterate;
>>>  	}
>>> @@ -1284,7 +1281,7 @@ static int do_update_counters(struct net *net, const char *name,
>>>  		return -ENOMEM;
>>>  
>>>  	t = find_table_lock(net, name, &ret, &ebt_mutex);
>>> -	if (!t)
>>> +	if (IS_ERR_OR_NULL(t))
>>>  		goto free_tmp;
>>>  
>>>  	if (num_counters != t->private->nentries) {
>>> @@ -1504,7 +1501,7 @@ static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>>>  		return -EFAULT;
>>>  
>>>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
>>> -	if (!t)
>>> +	if (IS_ERR_OR_NULL(t))
>>>  		return ret;
>>>  
>>>  	switch(cmd) {
>>> @@ -2319,7 +2316,7 @@ static int compat_do_ebt_get_ctl(struct sock *sk, int cmd,
>>>  		return -EFAULT;
>>>  
>>>  	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
>>> -	if (!t)
>>> +	if (IS_ERR_OR_NULL(t))
>>>  		return ret;
>>>  
>>>  	xt_compat_lock(NFPROTO_BRIDGE);
>>
>> .
>>
>

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Patch

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index ac78024..e7fe9f8 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -322,17 +322,14 @@  static inline void *
 find_inlist_lock_noload(struct list_head *head, const char *name, int *error,
    struct mutex *mutex)
 {
-	struct {
-		struct list_head list;
-		char name[EBT_FUNCTION_MAXNAMELEN];
-	} *e;
+	struct ebt_table *e;
 
 	*error = mutex_lock_interruptible(mutex);
 	if (*error != 0)
-		return NULL;
+		return ERR_PTR(-EINTR);
 
 	list_for_each_entry(e, head, list) {
-		if (strcmp(e->name, name) == 0)
+		 if (strcmp(e->name, name) == 0 && try_module_get(e->me))
 			return e;
 	}
 	*error = -ENOENT;
@@ -1005,7 +1002,7 @@  static int do_replace_finish(struct net *net, struct ebt_replace *repl,
 		goto free_counterstmp;
 
 	t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
-	if (!t) {
+	if (IS_ERR_OR_NULL(t)) {
 		ret = -ENOENT;
 		goto free_iterate;
 	}
@@ -1284,7 +1281,7 @@  static int do_update_counters(struct net *net, const char *name,
 		return -ENOMEM;
 
 	t = find_table_lock(net, name, &ret, &ebt_mutex);
-	if (!t)
+	if (IS_ERR_OR_NULL(t))
 		goto free_tmp;
 
 	if (num_counters != t->private->nentries) {
@@ -1504,7 +1501,7 @@  static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 		return -EFAULT;
 
 	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
-	if (!t)
+	if (IS_ERR_OR_NULL(t))
 		return ret;
 
 	switch(cmd) {
@@ -2319,7 +2316,7 @@  static int compat_do_ebt_get_ctl(struct sock *sk, int cmd,
 		return -EFAULT;
 
 	t = find_table_lock(net, tmp.name, &ret, &ebt_mutex);
-	if (!t)
+	if (IS_ERR_OR_NULL(t))
 		return ret;
 
 	xt_compat_lock(NFPROTO_BRIDGE);