Subject: Re: Linux 2.6.34-rc3 + CAN build problem

From: Oliver Hartkopp <[email-masked]>
Date: Sat, 10 Apr 2010 14:36:48 +0200

Németh Márton wrote:
> Eric Dumazet írta:
>> Le samedi 10 avril 2010 à 10:13 +0200, Németh Márton a écrit :
>>> Hi,
>>>
>>> I have some problem building Liunux kernel 2.6.34-rc3 with the attached .config:
>>>
>>> $ make clean bzImage modules
>>> [...]
>>>   CC      net/socket.o
>>>   LD      net/802/built-in.o
>>>   LD      net/can/built-in.o
>>>   CC [M]  net/can/bcm.o
>>>   CC [M]  net/can/raw.o
>>> In file included from /mnt/store/nmarci/src/linux-2.6.34-rc3/arch/x86/include/asm/uaccess.h:571,
>>>                  from include/net/checksum.h:25,
>>>                  from include/linux/skbuff.h:28,
>>>                  from include/linux/if_ether.h:124,
>>>                  from include/linux/netdevice.h:29,
>>>                  from net/can/raw.c:48:
>>> In function ‘copy_from_user’,
>>>     inlined from ‘raw_setsockopt’ at net/can/raw.c:447:
>>> /mnt/store/nmarci/src/linux-2.6.34-rc3/arch/x86/include/asm/uaccess_32.h:212: error: call to ‘copy_from_user_overflow’ declared with attribute error:
>>> copy_from_user() buffer size is not provably correct
>>> make[2]: *** [net/can/raw.o] Error 1
>>> make[1]: *** [net/can] Error 2
>>> make: *** [net] Error 2
>>>
>>>
>> Could you give us your compiler version ?
> 
> $ gcc --version
> gcc (Debian 4.4.2-9) 4.4.3 20100108 (prerelease)
> Copyright (C) 2009 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
>> Code is fine, but compiler a bit dumb :(
>>
>> [PATCH] can: avoids a false warning
>>
>> At this point optlen == sizeof(sfilter) but some compilers are dumb.
>>
>> Reported-by: Németh Márton <[email-masked]
>> Signed-off-by: Eric Dumazet <[email-masked]>

Acked-by: Oliver Hartkopp <[email-masked]>

Btw. i'm using the same compiler here (Debian Squeeze), and i did not have any
build problems with 2.6.24-rc3 and the following kernels like the currently
running 2.6.34-rc3-00288-gab195c5:

$ cat /proc/version
Linux version 2.6.34-rc3-00288-gab195c5 (hartko@vwagwolkf320) (gcc version
4.4.3 20100108 (prerelease) (Debian 4.4.2-9) ) #70 SMP Tue Apr 6 19:14:52 CEST
2010

So i wonder why Nemeth trapped into this problem ... probably an include file
mix-up?

Regards,
Oliver

>> ---
>> diff --git a/net/can/raw.c b/net/can/raw.c
>> index 3a7dffb..da99cf1 100644
>> --- a/net/can/raw.c
>> +++ b/net/can/raw.c
>> @@ -445,7 +445,7 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
>>  				return -EFAULT;
>>  			}
>>  		} else if (count == 1) {
>> -			if (copy_from_user(&sfilter, optval, optlen))
>> +			if (copy_from_user(&sfilter, optval, sizeof(sfilter)))
>>  				return -EFAULT;
>>  		}
>>  
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