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Sat, 12 Sep 2026 20:47:34 -0700 (PDT) X-Received: by 2002:a05:622a:1c0e:b0:530:f84c:efc7 with SMTP id d75a77b69052e-530f84cfebbmr32873081cf.25.1789271253860; Sat, 12 Sep 2026 20:47:33 -0700 (PDT) Received: from [172.31.1.12] ([70.105.247.246]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f2032d4sm60952136d6.5.2026.09.12.20.47.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 12 Sep 2026 20:47:33 -0700 (PDT) Message-ID: <8fb9c70b-bb77-4dd5-8939-6116eb99ec25@redhat.com> Date: Sat, 12 Sep 2026 23:47:24 -0400 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] fsidd: require root credentials on abstract socket To: Olga Kornievskaia Cc: linux-nfs@vger.kernel.org References: <20260907011328.21425-1-okorniev@redhat.com> Content-Language: en-US From: Steve Dickson In-Reply-To: <20260907011328.21425-1-okorniev@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/6/26 9:13 PM, Olga Kornievskaia wrote: > fsidd listens on an abstract UNIX domain socket which has no > filesystem-level access control.  Any local unprivileged user can > connect and issue mutating commands (get_or_create_fsidnum) that > grow the reexport database without limit, degrading mountd > performance. > > Add a SO_PEERCRED check to reject connections from non-root > clients.  The only legitimate client is mountd, which runs as root. > > Fixes: 6fd2732d ("export: Add fsidd") > Signed-off-by: Olga Kornievskaia > --- > support/reexport/fsidd.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/support/reexport/fsidd.c b/support/reexport/fsidd.c > index 9b80b451..c714386e 100644 > --- a/support/reexport/fsidd.c > +++ b/support/reexport/fsidd.c > @@ -7,6 +7,7 @@ > #include > #endif > #include > +#include > #include > #include > > @@ -147,6 +148,8 @@ static void srv_cb(evutil_socket_t fd, short ev, void *d) > { > int cl = accept4(fd, NULL, NULL, SOCK_NONBLOCK); > struct event *client_ev; > + struct ucred cred; > + socklen_t clen = sizeof(cred); > > if (cl == -1) { > if (errno == EMFILE || errno == ENFILE || errno == ENOMEM || > @@ -162,6 +165,12 @@ static void srv_cb(evutil_socket_t fd, short ev, void *d) > (void)ev; > (void)d; > > + if (getsockopt(cl, SOL_SOCKET, SO_PEERCRED, &cred, &clen) < 0 || > + cred.uid != 0) { > + close(cl); > + return; > + } > + > client_ev = event_new(evbase, cl, EV_READ | EV_PERSIST | EV_CLOSED, client_cb, event_self_cbarg()); > if (!client_ev || event_add(client_ev, NULL) == -1) { > if (client_ev) This didn't apply cleanly... so I'll deal with it with some other upcoming fsidd patches steved.