Re: [PATCHv3 net] sock_diag: request _diag module only when the family or proto has been registered

[David Miller <davem@davemloft.net>]

From: Xin Long <lucien.xin@gmail.com>
Date: Sat, 10 Mar 2018 18:57:50 +0800

> Now when using 'ss' in iproute, kernel would try to load all _diag
> modules, which also causes corresponding family and proto modules
> to be loaded as well due to module dependencies.
> 
> Like after running 'ss', sctp, dccp, af_packet (if it works as a module)
> would be loaded.
> 
> For example:
> 
>   $ lsmod|grep sctp
>   $ ss
>   $ lsmod|grep sctp
>   sctp_diag              16384  0
>   sctp                  323584  5 sctp_diag
>   inet_diag              24576  4 raw_diag,tcp_diag,sctp_diag,udp_diag
>   libcrc32c              16384  3 nf_conntrack,nf_nat,sctp
> 
> As these family and proto modules are loaded unintentionally, it
> could cause some problems, like:
> 
> - Some debug tools use 'ss' to collect the socket info, which loads all
>   those diag and family and protocol modules. It's noisy for identifying
>   issues.
> 
> - Users usually expect to drop sctp init packet silently when they
>   have no sense of sctp protocol instead of sending abort back.
> 
> - It wastes resources (especially with multiple netns), and SCTP module
>   can't be unloaded once it's loaded.
> 
> ...
> 
> In short, it's really inappropriate to have these family and proto
> modules loaded unexpectedly when just doing debugging with inet_diag.
> 
> This patch is to introduce sock_load_diag_module() where it loads
> the _diag module only when it's corresponding family or proto has
> been already registered.
> 
> Note that we can't just load _diag module without the family or
> proto loaded, as some symbols used in _diag module are from the
> family or proto module.
> 
> v1->v2:
>   - move inet proto check to inet_diag to avoid a compiling err.
> v2->v3:
>   - define sock_load_diag_module in sock.c and export one symbol
>     only.
>   - improve the changelog.
> 
> Reported-by: Sabrina Dubroca <sd@queasysnail.net>
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Acked-by: Phil Sutter <phil@nwl.cc>
> Acked-by: Sabrina Dubroca <sd@queasysnail.net>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Ok, applied and queued up for -stable, thanks.