Re: [PATCH nfs-utils 1/2] fsidd: call anonymous sockets by their name only, don't fill with NULs to 108 bytes

[Richard Weinberger <richard@nod.at>]

----- Ursprüngliche Mail -----
> Von: "Salvatore Bonaccorso" <carnil@debian.org>
> An: "NeilBrown" <neilb@suse.de>, "richard" <richard@nod.at>, "Steve Dickson" <steved@redhat.com>
> CC: "Ahelenia Ziemiańska" <nabijaczleweli@nabijaczleweli.xyz>, "linux-nfs" <linux-nfs@vger.kernel.org>
> Gesendet: Dienstag, 21. November 2023 20:58:45
> Betreff: Re: [PATCH nfs-utils 1/2] fsidd: call anonymous sockets by their name only, don't fill with NULs to 108 bytes

> Hi,
> 
> Explicitly CC'ing people involved for the e00ab3c0616f ("fsidd:
> provide better default socket name.") change:
> 
> On Sun, Sep 03, 2023 at 05:21:52PM +0200, Ahelenia Ziemiańska wrote:
>> Since e00ab3c0616fe6d83ab0710d9e7d989c299088f7, ss -l looks like this:
>>   u_seq               LISTEN                0                     5
>>   @/run/fsid.sock@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
>>   26989379                                                       * 0
>> with fsidd pushing all the addresses to 108 bytes wide, which is deeply
>> egregious if you don't filter it out and recolumnate.
>> 
>> This is because, naturally (unix(7)), "Null bytes in the name have
>> no special significance": abstract addresses are binary blobs, but
>> paths automatically terminate at the first NUL byte, since paths
>> can't contain those.
>> 
>> So just specify the correct address length when we're using the abstract domain:
>> unix(7) recommends "offsetof(struct sockaddr_un, sun_path) + strlen(sun_path) +
>> 1"
>> for paths, but we don't want to include the terminating NUL, so it's just
>> "offsetof(struct sockaddr_un, sun_path) + strlen(sun_path)".
>> This brings the width back to order:
>> -- >8 --
>> $ ss -la | grep @
>> u_str ESTAB     0      0
>> @45208536ec96909a/bus/systemd-timesyn/bus-api-timesync 18500238
>> * 18501249
>> u_str ESTAB     0      0
>> @fecc9657d2315eb7/bus/systemd-network/bus-api-network 18495452
>> * 18494406
>> u_seq LISTEN    0      5
>> @/run/fsid.sock 27168796
>> * 0
>> u_str ESTAB     0      0
>> @ac308f35f50797a2/bus/systemd-logind/system 19406
>> * 15153
>> u_str ESTAB     0      0
>> @b6606e0dfacbae75/bus/systemd/bus-api-system 18494353
>> * 18495334
>> u_str ESTAB     0      0
>> @5880653d215718a7/bus/systemd/bus-system 26930876
>> * 26930003
>> -- >8 --
>> 
>> Fixes: e00ab3c0616fe6d83ab0710d9e7d989c299088f7 ("fsidd: provide
>>  better default socket name.")
>> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
>> ---
>>  support/reexport/fsidd.c    | 8 +++++---
>>  support/reexport/reexport.c | 7 +++++--
>>  2 files changed, 10 insertions(+), 5 deletions(-)
>> 
>> diff --git a/support/reexport/fsidd.c b/support/reexport/fsidd.c
>> index d4b245e8..4c377415 100644
>> --- a/support/reexport/fsidd.c
>> +++ b/support/reexport/fsidd.c
>> @@ -171,10 +171,12 @@ int main(void)
>>  	memset(&addr, 0, sizeof(struct sockaddr_un));
>>  	addr.sun_family = AF_UNIX;
>>  	strncpy(addr.sun_path, sock_file, sizeof(addr.sun_path) - 1);
>> -	if (addr.sun_path[0] == '@')
>> +	socklen_t addr_len = sizeof(struct sockaddr_un);
>> +	if (addr.sun_path[0] == '@') {
>>  		/* "abstract" socket namespace */
>> +		addr_len = offsetof(struct sockaddr_un, sun_path) + strlen(addr.sun_path);
>>  		addr.sun_path[0] = 0;
>> -	else
>> +	} else
>>  		unlink(sock_file);
>>  
>>  	srv = socket(AF_UNIX, SOCK_SEQPACKET | SOCK_NONBLOCK, 0);
>> @@ -183,7 +185,7 @@ int main(void)
>>  		return 1;
>>  	}
>>  
>> -	if (bind(srv, (const struct sockaddr *)&addr, sizeof(struct sockaddr_un)) ==
>> -1) {
>> +	if (bind(srv, (const struct sockaddr *)&addr, addr_len) == -1) {
>>  		xlog(L_WARNING, "Unable to bind %s: %m\n", sock_file);
>>  		return 1;
>>  	}
>> diff --git a/support/reexport/reexport.c b/support/reexport/reexport.c
>> index d9a700af..b7ee6f46 100644
>> --- a/support/reexport/reexport.c
>> +++ b/support/reexport/reexport.c
>> @@ -40,9 +40,12 @@ static bool connect_fsid_service(void)
>>  	memset(&addr, 0, sizeof(struct sockaddr_un));
>>  	addr.sun_family = AF_UNIX;
>>  	strncpy(addr.sun_path, sock_file, sizeof(addr.sun_path) - 1);
>> -	if (addr.sun_path[0] == '@')
>> +	socklen_t addr_len = sizeof(struct sockaddr_un);
>> +	if (addr.sun_path[0] == '@') {
>>  		/* "abstract" socket namespace */
>> +		addr_len = offsetof(struct sockaddr_un, sun_path) + strlen(addr.sun_path);
>>  		addr.sun_path[0] = 0;
>> +	}
>>  
>>  	s = socket(AF_UNIX, SOCK_SEQPACKET, 0);
>>  	if (s == -1) {
>> @@ -50,7 +53,7 @@ static bool connect_fsid_service(void)
>>  		return false;
>>  	}
>>  
>> -	ret = connect(s, (const struct sockaddr *)&addr, sizeof(struct sockaddr_un));
>> +	ret = connect(s, (const struct sockaddr *)&addr, addr_len);
>>  	if (ret == -1) {
>>  		xlog(L_WARNING, "Unable to connect %s: %m, is fsidd running?\n", sock_file);
>>  		return false;
>> --
>> 2.40.1
> 
> Did this one felt trough the cracks?

At least it never hit my inbox.
Change looks good to me.

Thanks,
//richard