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From: "NeilBrown" <neilb@suse.de>
To: "Olga Kornievskaia" <aglo@umich.edu>
Cc: Ahelenia =?utf-8?q?Ziemia=C5=84ska?= <nabijaczleweli@nabijaczleweli.xyz>,
 linux-nfs@vger.kernel.org, "Steve Dickson" <steved@redhat.com>
Subject: Re: [PATCH nfs-utils v2 1/2] fsidd: call anonymous sockets by their
 name only, don't fill with NULs to 108 bytes
In-reply-to:
 <CAN-5tyGfu9xcFHwD7G5+Hkan=19H1mmWenBm+g75M-uUwzzU7Q@mail.gmail.com>
References: =?utf-8?q?=3Cb38ecca96762d939d377c381bf34521ee5945129=2E17006011?=
 =?utf-8?q?99=2Egit=2Enabijaczleweli=40nabijaczleweli=2Exyz=3E=2C?=
 <CAN-5tyGfu9xcFHwD7G5+Hkan=19H1mmWenBm+g75M-uUwzzU7Q@mail.gmail.com>
Date: Fri, 08 Dec 2023 11:08:39 +1100
Message-id: <170199411925.12910.14964427409507748000@noble.neil.brown.name>

On Thu, 07 Dec 2023, Olga Kornievskaia wrote:
> On Tue, Nov 21, 2023 at 4:15=E2=80=AFPM Ahelenia Ziemia=C5=84ska
> <nabijaczleweli@nabijaczleweli.xyz> 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_p=
ath) + 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-a=
pi-timesync 18500238                            * 18501249
> > u_str ESTAB     0      0       @fecc9657d2315eb7/bus/systemd-network/bus-=
api-network 18495452                            * 18494406
> > u_seq LISTEN    0      5                                             @/ru=
n/fsid.sock 27168796                            * 0
> > u_str ESTAB     0      0                 @ac308f35f50797a2/bus/systemd-lo=
gind/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 Ziemia=C5=84ska <nabijaczleweli@nabijaczleweli.xy=
z>
> > ---
> > v1: <04f3fe71defa757d518468f04f08334a5d0dfbb9.1693754442.git.nabijaczlewe=
li@nabijaczleweli.xyz>
> > v2 NFC, addr_len declared at top of function
> >
> >  support/reexport/fsidd.c    | 9 ++++++---
> >  support/reexport/reexport.c | 8 ++++++--
> >  2 files changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/support/reexport/fsidd.c b/support/reexport/fsidd.c
> > index 3e62b3fc..8a70b78f 100644
> > --- a/support/reexport/fsidd.c
> > +++ b/support/reexport/fsidd.c
> > @@ -147,6 +147,7 @@ int main(void)
> >  {
> >         struct event *srv_ev;
> >         struct sockaddr_un addr;
> > +       socklen_t addr_len;
> >         char *sock_file;
> >         int srv;
> >
> > @@ -161,10 +162,12 @@ int main(void)
> >         memset(&addr, 0, sizeof(struct sockaddr_un));
> >         addr.sun_family =3D AF_UNIX;
> >         strncpy(addr.sun_path, sock_file, sizeof(addr.sun_path) - 1);
> > -       if (addr.sun_path[0] =3D=3D '@')
> > +       addr_len =3D sizeof(struct sockaddr_un);
> > +       if (addr.sun_path[0] =3D=3D '@') {
> >                 /* "abstract" socket namespace */
> > +               addr_len =3D offsetof(struct sockaddr_un, sun_path) + str=
len(addr.sun_path);
> >                 addr.sun_path[0] =3D 0;
> > -       else
> > +       } else
> >                 unlink(sock_file);
> >
> >         srv =3D socket(AF_UNIX, SOCK_SEQPACKET | SOCK_NONBLOCK, 0);
> > @@ -173,7 +176,7 @@ int main(void)
> >                 return 1;
> >         }
> >
> > -       if (bind(srv, (const struct sockaddr *)&addr, sizeof(struct socka=
ddr_un)) =3D=3D -1) {
> > +       if (bind(srv, (const struct sockaddr *)&addr, addr_len) =3D=3D -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 78516586..0fb49a46 100644
> > --- a/support/reexport/reexport.c
> > +++ b/support/reexport/reexport.c
> > @@ -21,6 +21,7 @@ static int fsidd_srv =3D -1;
> >  static bool connect_fsid_service(void)
> >  {
> >         struct sockaddr_un addr;
> > +       socklen_t addr_len;
> >         char *sock_file;
> >         int ret;
> >         int s;
> > @@ -33,9 +34,12 @@ static bool connect_fsid_service(void)
> >         memset(&addr, 0, sizeof(struct sockaddr_un));
> >         addr.sun_family =3D AF_UNIX;
> >         strncpy(addr.sun_path, sock_file, sizeof(addr.sun_path) - 1);
> > -       if (addr.sun_path[0] =3D=3D '@')
> > +       addr_len =3D sizeof(struct sockaddr_un);
> > +       if (addr.sun_path[0] =3D=3D '@') {
> >                 /* "abstract" socket namespace */
> > +               addr_len =3D offsetof(struct sockaddr_un, sun_path) + str=
len(addr.sun_path);
> >                 addr.sun_path[0] =3D 0;
> > +       }
> >
> >         s =3D socket(AF_UNIX, SOCK_SEQPACKET, 0);
> >         if (s =3D=3D -1) {
> > @@ -43,7 +47,7 @@ static bool connect_fsid_service(void)
> >                 return false;
> >         }
> >
> > -       ret =3D connect(s, (const struct sockaddr *)&addr, sizeof(struct =
sockaddr_un));
> > +       ret =3D connect(s, (const struct sockaddr *)&addr, addr_len);
> >         if (ret =3D=3D -1) {
> >                 xlog(L_WARNING, "Unable to connect %s: %m, is fsidd runni=
ng?\n", sock_file);
> >                 return false;
> > --
> > 2.39.2
> >
>=20
> Hi folks,
>=20
> I'm hitting the following compile error (in RHEL9.2). I believe the
> code is missing an include for stddef.h. When I add it, things
> compile. I'll submit a patch.
>=20
> gcc -DHAVE_CONFIG_H -I. -I../../support/include  -I/usr/include/tirpc
> -D_GNU_SOURCE -pipe  -Wall  -Wextra  -Werror=3Dstrict-prototypes
> -Werror=3Dmissing-prototypes  -Werror=3Dmissing-declarations
> -Werror=3Dformat=3D2  -Werror=3Dundef  -Werror=3Dmissing-include-dirs
> -Werror=3Dstrict-aliasing=3D2  -Werror=3Dinit-self
> -Werror=3Dimplicit-function-declaration  -Werror=3Dreturn-type
> -Werror=3Dswitch  -Werror=3Doverflow  -Werror=3Dparentheses
> -Werror=3Daggregate-return  -Werror=3Dunused-result  -fno-strict-aliasing
> -Werror=3Dformat-overflow=3D2 -Werror=3Dint-conversion
> -Werror=3Dincompatible-pointer-types -Werror=3Dmisleading-indentation
> -Wno-cast-function-type -g -O2 -MT reexport.o -MD -MP -MF
> .deps/reexport.Tpo -c -o reexport.o reexport.c
> reexport.c: In function =E2=80=98connect_fsid_service=E2=80=99:
> reexport.c:40:28: error: implicit declaration of function =E2=80=98offsetof=
=E2=80=99
> [-Werror=3Dimplicit-function-declaration]
>    40 |                 addr_len =3D offsetof(struct sockaddr_un,
> sun_path) + strlen(addr.sun_path);
>       |                            ^~~~~~~~
> reexport.c:18:1: note: =E2=80=98offsetof=E2=80=99 is defined in header =E2=
=80=98<stddef.h>=E2=80=99;
> did you forget to =E2=80=98#include <stddef.h>=E2=80=99?
>    17 | #include "xlog.h"
>   +++ |+#include <stddef.h>
>    18 |
> reexport.c:40:37: error: expected expression before =E2=80=98struct=E2=80=99
>    40 |                 addr_len =3D offsetof(struct sockaddr_un,
> sun_path) + strlen(addr.sun_path);
>       |                                     ^~~~~~
> cc1: some warnings being treated as errors
> make[2]: *** [Makefile:529: reexport.o] Error 1
> make[2]: Leaving directory '/home/aglo/nfs-utils/support/reexport'
> make[1]: *** [Makefile:448: all-recursive] Error 1
> make[1]: Leaving directory '/home/aglo/nfs-utils/support'
>=20


Interesting - in openSUSE, dlfcn.h includes stddef.h, which is why the
compile works for me.   Obviously we cannot rely on that.

reexport.c and fsidd.c will both need stddef.

Thanks!

NeilBrown