[PATCH] SUNRPC: Fix -Wformat-truncation warning

[PATCH] SUNRPC: Fix -Wformat-truncation warning

[kunwu.chan]

From: Kunwu Chan <chentao@kylinos.cn>

Increase size of the servername array to avoid truncated output warning.

net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
writing up to 107 bytes into a region of size 48
[-Werror=format-truncation=]
  582 |                   snprintf(servername, sizeof(servername), "%s",
      |                                                             ^~

net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
between 1 and 108 bytes into a destination of size 48
  582 |                     snprintf(servername, sizeof(servername), "%s",
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  583 |                                          sun->sun_path);

Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
---
 net/sunrpc/clnt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 09f29a95f2bc..874085f3ed50 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
 		.connect_timeout = args->connect_timeout,
 		.reconnect_timeout = args->reconnect_timeout,
 	};
-	char servername[48];
+	char servername[108];
 	struct rpc_clnt *clnt;
 	int i;
 
-- 
2.40.1

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[NeilBrown]

On Wed, 14 Aug 2024, kunwu.chan@linux.dev wrote:
> From: Kunwu Chan <chentao@kylinos.cn>
> 
> Increase size of the servername array to avoid truncated output warning.
> 
> net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
> writing up to 107 bytes into a region of size 48
> [-Werror=format-truncation=]
>   582 |                   snprintf(servername, sizeof(servername), "%s",
>       |                                                             ^~
> 
> net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
> between 1 and 108 bytes into a destination of size 48
>   582 |                     snprintf(servername, sizeof(servername), "%s",
>       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   583 |                                          sun->sun_path);
> 
> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
> ---
>  net/sunrpc/clnt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 09f29a95f2bc..874085f3ed50 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
>  		.connect_timeout = args->connect_timeout,
>  		.reconnect_timeout = args->reconnect_timeout,
>  	};
> -	char servername[48];
> +	char servername[108];

If we choose this approach to removing the warning, then we should use
UNIX_PATH_MAX rather than 108.

However the longest server name copied in here will in practice be
   /var/run/rpcbind.sock

so the extra 60 bytes on the stack is wasted ...  maybe that doesn't
matter.

The string is only used by xprt_create_transport() which requires it to
be less than RPC_MAXNETNAMELEN - which is 256.
So maybe that would be a better value to use for the array size ....  if
we assume that stack space isn't a problem.

What ever number we use, I'd rather it was a defined constant, and not
an apparently arbitrary number.

Thanks,
NeilBrown


>  	struct rpc_clnt *clnt;
>  	int i;
>  
> -- 
> 2.40.1
> 
> 

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[Kunwu Chan]

Thanks for your reply.

On 2024/8/14 18:28, NeilBrown wrote:
> On Wed, 14 Aug 2024, kunwu.chan@linux.dev wrote:
>> From: Kunwu Chan <chentao@kylinos.cn>
>>
>> Increase size of the servername array to avoid truncated output warning.
>>
>> net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
>> writing up to 107 bytes into a region of size 48
>> [-Werror=format-truncation=]
>>    582 |                   snprintf(servername, sizeof(servername), "%s",
>>        |                                                             ^~
>>
>> net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
>> between 1 and 108 bytes into a destination of size 48
>>    582 |                     snprintf(servername, sizeof(servername), "%s",
>>        |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    583 |                                          sun->sun_path);
>>
>> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
>> ---
>>   net/sunrpc/clnt.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
>> index 09f29a95f2bc..874085f3ed50 100644
>> --- a/net/sunrpc/clnt.c
>> +++ b/net/sunrpc/clnt.c
>> @@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
>>   		.connect_timeout = args->connect_timeout,
>>   		.reconnect_timeout = args->reconnect_timeout,
>>   	};
>> -	char servername[48];
>> +	char servername[108];
> If we choose this approach to removing the warning, then we should use
> UNIX_PATH_MAX rather than 108.
My negligence.
>
> However the longest server name copied in here will in practice be
>     /var/run/rpcbind.sock
>
> so the extra 60 bytes on the stack is wasted ...  maybe that doesn't
> matter.
I'm thinking  about use a dynamic space alloc method like kasprintf to 
avoid space waste.
> The string is only used by xprt_create_transport() which requires it to
> be less than RPC_MAXNETNAMELEN - which is 256.
> So maybe that would be a better value to use for the array size ....  if
> we assume that stack space isn't a problem.

Thank you for the detailed explanation. I read the 
xprt_create_transport,  the RPC_MAXNETNAMELEN

is only use to xprt_create_transport .

> What ever number we use, I'd rather it was a defined constant, and not
> an apparently arbitrary number.

Whether we could check the sun->sun_path length before using snprintf?  
The array size should smaller

than  the minimum of sun->sun_path and RPC_MAXNETNAMELEN.

Or use the dynamic space allocate method to save space.

>
> Thanks,
> NeilBrown
>
>
>>   	struct rpc_clnt *clnt;
>>   	int i;
>>   
>> -- 
>> 2.40.1
>>
>>
-- 
Thanks,
   Kunwu.Chan

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[NeilBrown]

On Thu, 15 Aug 2024, Kunwu Chan wrote:
> Thanks for your reply.
> 
> On 2024/8/14 18:28, NeilBrown wrote:
> > On Wed, 14 Aug 2024, kunwu.chan@linux.dev wrote:
> >> From: Kunwu Chan <chentao@kylinos.cn>
> >>
> >> Increase size of the servername array to avoid truncated output warning.
> >>
> >> net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
> >> writing up to 107 bytes into a region of size 48
> >> [-Werror=format-truncation=]
> >>    582 |                   snprintf(servername, sizeof(servername), "%s",
> >>        |                                                             ^~
> >>
> >> net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
> >> between 1 and 108 bytes into a destination of size 48
> >>    582 |                     snprintf(servername, sizeof(servername), "%s",
> >>        |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >>    583 |                                          sun->sun_path);
> >>
> >> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
> >> ---
> >>   net/sunrpc/clnt.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> >> index 09f29a95f2bc..874085f3ed50 100644
> >> --- a/net/sunrpc/clnt.c
> >> +++ b/net/sunrpc/clnt.c
> >> @@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
> >>   		.connect_timeout = args->connect_timeout,
> >>   		.reconnect_timeout = args->reconnect_timeout,
> >>   	};
> >> -	char servername[48];
> >> +	char servername[108];
> > If we choose this approach to removing the warning, then we should use
> > UNIX_PATH_MAX rather than 108.
> My negligence.
> >
> > However the longest server name copied in here will in practice be
> >     /var/run/rpcbind.sock
> >
> > so the extra 60 bytes on the stack is wasted ...  maybe that doesn't
> > matter.
> I'm thinking  about use a dynamic space alloc method like kasprintf to 
> avoid space waste.
> > The string is only used by xprt_create_transport() which requires it to
> > be less than RPC_MAXNETNAMELEN - which is 256.
> > So maybe that would be a better value to use for the array size ....  if
> > we assume that stack space isn't a problem.
> 
> Thank you for the detailed explanation. I read the 
> xprt_create_transport,  the RPC_MAXNETNAMELEN
> 
> is only use to xprt_create_transport .
> 
> > What ever number we use, I'd rather it was a defined constant, and not
> > an apparently arbitrary number.
> 
> Whether we could check the sun->sun_path length before using snprintf?  
> The array size should smaller
> 
> than  the minimum of sun->sun_path and RPC_MAXNETNAMELEN.
> 
> Or use the dynamic space allocate method to save space.

I think that dynamically allocating space is not a good idea.  It means
you have to handle failure which is just a waste of code.

I'd suggest simply changing the array to RPC_MAXNETNAMELEN.

NeilBrown



> 
> >
> > Thanks,
> > NeilBrown
> >
> >
> >>   	struct rpc_clnt *clnt;
> >>   	int i;
> >>   
> >> -- 
> >> 2.40.1
> >>
> >>
> -- 
> Thanks,
>    Kunwu.Chan
> 
> 

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[Kunwu Chan]

Thanks for your reply.

On 2024/8/15 19:39, NeilBrown wrote:
> On Thu, 15 Aug 2024, Kunwu Chan wrote:
>> Thanks for your reply.
>>
>> On 2024/8/14 18:28, NeilBrown wrote:
>>> On Wed, 14 Aug 2024, kunwu.chan@linux.dev wrote:
>>>> From: Kunwu Chan <chentao@kylinos.cn>
>>>>
>>>> Increase size of the servername array to avoid truncated output warning.
>>>>
>>>> net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
>>>> writing up to 107 bytes into a region of size 48
>>>> [-Werror=format-truncation=]
>>>>     582 |                   snprintf(servername, sizeof(servername), "%s",
>>>>         |                                                             ^~
>>>>
>>>> net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
>>>> between 1 and 108 bytes into a destination of size 48
>>>>     582 |                     snprintf(servername, sizeof(servername), "%s",
>>>>         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>     583 |                                          sun->sun_path);
>>>>
>>>> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
>>>> ---
>>>>    net/sunrpc/clnt.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
>>>> index 09f29a95f2bc..874085f3ed50 100644
>>>> --- a/net/sunrpc/clnt.c
>>>> +++ b/net/sunrpc/clnt.c
>>>> @@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
>>>>    		.connect_timeout = args->connect_timeout,
>>>>    		.reconnect_timeout = args->reconnect_timeout,
>>>>    	};
>>>> -	char servername[48];
>>>> +	char servername[108];
>>> If we choose this approach to removing the warning, then we should use
>>> UNIX_PATH_MAX rather than 108.
>> My negligence.
>>> However the longest server name copied in here will in practice be
>>>      /var/run/rpcbind.sock
>>>
>>> so the extra 60 bytes on the stack is wasted ...  maybe that doesn't
>>> matter.
>> I'm thinking  about use a dynamic space alloc method like kasprintf to
>> avoid space waste.
>>> The string is only used by xprt_create_transport() which requires it to
>>> be less than RPC_MAXNETNAMELEN - which is 256.
>>> So maybe that would be a better value to use for the array size ....  if
>>> we assume that stack space isn't a problem.
>> Thank you for the detailed explanation. I read the
>> xprt_create_transport,  the RPC_MAXNETNAMELEN
>>
>> is only use to xprt_create_transport .
>>
>>> What ever number we use, I'd rather it was a defined constant, and not
>>> an apparently arbitrary number.
>> Whether we could check the sun->sun_path length before using snprintf?
>> The array size should smaller
>>
>> than  the minimum of sun->sun_path and RPC_MAXNETNAMELEN.
>>
>> Or use the dynamic space allocate method to save space.
> I think that dynamically allocating space is not a good idea.  It means
> you have to handle failure which is just a waste of code.
>
> I'd suggest simply changing the array to RPC_MAXNETNAMELEN.
I'll follow your suggestion and change it in v2.
>
> NeilBrown
>
>
>
>>> Thanks,
>>> NeilBrown
>>>
>>>
>>>>    	struct rpc_clnt *clnt;
>>>>    	int i;
>>>>    
>>>> -- 
>>>> 2.40.1
>>>>
>>>>
>> -- 
>> Thanks,
>>     Kunwu.Chan
>>
>>
-- 
Thanks,
   Kunwu.Chan

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[Andrew Lunn]

On Wed, Aug 14, 2024 at 05:38:53PM +0800, kunwu.chan@linux.dev wrote:
> From: Kunwu Chan <chentao@kylinos.cn>
> 
> Increase size of the servername array to avoid truncated output warning.
> 
> net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
> writing up to 107 bytes into a region of size 48
> [-Werror=format-truncation=]
>   582 |                   snprintf(servername, sizeof(servername), "%s",
>       |                                                             ^~
> 
> net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
> between 1 and 108 bytes into a destination of size 48
>   582 |                     snprintf(servername, sizeof(servername), "%s",
>       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   583 |                                          sun->sun_path);

I think this has come up before, but i could be mis-remembering.
Please could you do a search for the discussion. The fact it is not
solved suggests to me it is not so simple to fix. Maybe there is some
protocol implications here.

       Andrew

Re: [PATCH] SUNRPC: Fix -Wformat-truncation warning

[NeilBrown]

On Sat, 17 Aug 2024, Andrew Lunn wrote:
> On Wed, Aug 14, 2024 at 05:38:53PM +0800, kunwu.chan@linux.dev wrote:
> > From: Kunwu Chan <chentao@kylinos.cn>
> > 
> > Increase size of the servername array to avoid truncated output warning.
> > 
> > net/sunrpc/clnt.c:582:75: error：‘%s’ directive output may be truncated
> > writing up to 107 bytes into a region of size 48
> > [-Werror=format-truncation=]
> >   582 |                   snprintf(servername, sizeof(servername), "%s",
> >       |                                                             ^~
> > 
> > net/sunrpc/clnt.c:582:33: note:‘snprintf’ output
> > between 1 and 108 bytes into a destination of size 48
> >   582 |                     snprintf(servername, sizeof(servername), "%s",
> >       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   583 |                                          sun->sun_path);
> 
> I think this has come up before, but i could be mis-remembering.
> Please could you do a search for the discussion. The fact it is not
> solved suggests to me it is not so simple to fix. Maybe there is some
> protocol implications here.
> 
>        Andrew
> 

All I could find was 

 https://lore.kernel.org/all/1648103566-15528-1-git-send-email-baihaowen@meizu.com/

which essentially followed the same path as this conversation.  The
patch was resubmitted using UNIX_PATH_MAX but never responded to by the
relevant maintainers.

There are no protocol implications.  This string is only used for
informational messages.

NeilBrown