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

From: Németh Márton <[email-masked]>
Date: Sat, 10 Apr 2010 12:36:30 +0200

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]>
> ---
> 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;
>  		}
>  
> 
> 
> 
>