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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id z11sm5802732pfk.46.2020.07.01.06.46.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2020 06:46:36 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 69D5F403DC; Wed, 1 Jul 2020 13:46:35 +0000 (UTC) Date: Wed, 1 Jul 2020 13:46:35 +0000 From: Luis Chamberlain To: Christian Borntraeger , Jessica Yu , Tetsuo Handa Cc: Christoph Hellwig , "Eric W. Biederman" , Andrew Morton , ast@kernel.org, axboe@kernel.dk, bfields@fieldses.org, bridge@lists.linux-foundation.org, chainsaw@gentoo.org, christian.brauner@ubuntu.com, chuck.lever@oracle.com, davem@davemloft.net, dhowells@redhat.com, gregkh@linuxfoundation.org, jarkko.sakkinen@linux.intel.com, jmorris@namei.org, josh@joshtriplett.org, keescook@chromium.org, keyrings@vger.kernel.org, kuba@kernel.org, lars.ellenberg@linbit.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-security-module@vger.kernel.org, nikolay@cumulusnetworks.com, philipp.reisner@linbit.com, ravenexp@gmail.com, roopa@cumulusnetworks.com, serge@hallyn.com, slyfox@gentoo.org, viro@zeniv.linux.org.uk, yangtiezhu@loongson.cn, netdev@vger.kernel.org, markward@linux.ibm.com, linux-s390 Subject: Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used seems to break linux bridge on s390x (bisected) Message-ID: <20200701134635.GR4332@42.do-not-panic.com> References: <20200624144311.GA5839@infradead.org> <9e767819-9bbe-2181-521e-4d8ca28ca4f7@de.ibm.com> <20200624160953.GH4332@42.do-not-panic.com> <4e27098e-ac8d-98f0-3a9a-ea25242e24ec@de.ibm.com> <4d8fbcea-a892-3453-091f-d57c03f9aa90@de.ibm.com> <1263e370-7cee-24d8-b98c-117bf7c90a83@de.ibm.com> <20200626025410.GJ4332@42.do-not-panic.com> <20200630175704.GO13911@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Wed, Jul 01, 2020 at 12:08:11PM +0200, Christian Borntraeger wrote: > dmesg attached > [ 14.438482] virbr0: port 1(virbr0-nic) entered blocking state > [ 14.438485] virbr0: port 1(virbr0-nic) entered disabled state > [ 14.438635] device virbr0-nic entered promiscuous mode > [ 14.439654] umh: sub_info->path: /sbin/bridge-stp > [ 14.439656] /sbin/bridge-stp > [ 14.439656] virbr0 > [ 14.439656] start OK so what we seem to want to debug is the umh call for: /sbin/bridge-stp virbr0 start > [ 14.439734] == ret: 00 > [ 14.439735] == KWIFEXITED(ret): 01 > [ 14.439736] KWEXITSTATUS(ret): 0 Its not clear if this is the respective return value, but now that we have a clue that this is the the only non-modprobe call, we should have a clearer certainty that this is the issue. Indeed my patch "umh: fix processed error when UMH_WAIT_PROC is used" did modify bridge-stp in the following way: diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c index ba55851fe132..bdd94b45396b 100644 --- a/net/bridge/br_stp_if.c +++ b/net/bridge/br_stp_if.c @@ -133,14 +133,8 @@ static int br_stp_call_user(struct net_bridge *br, char *arg) /* call userspace STP and report program errors */ rc = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC); - if (rc > 0) { - if (rc & 0xff) - br_debug(br, BR_STP_PROG " received signal %d\n", - rc & 0x7f); - else - br_debug(br, BR_STP_PROG " exited with code %d\n", - (rc >> 8) & 0xff); - } + if (rc != 0) + br_debug(br, BR_STP_PROG " failed with exit code %d\n", rc); return rc; } If you look at this carefully though you'll notice that the change just modifies *when* we issue the debug print. The more important relevant part of the patch however was that we now do return a correct error value when the call fails. More importantly, depending on if an error or not we run the kernel STP or userspace STP later: static void br_stp_start(struct net_bridge *br) { int err = -ENOENT; if (net_eq(dev_net(br->dev), &init_net)) err = br_stp_call_user(br, "start"); if (err && err != -ENOENT) br_err(br, "failed to start userspace STP (%d)\n", err); spin_lock_bh(&br->lock); if (br->bridge_forward_delay < BR_MIN_FORWARD_DELAY) __br_set_forward_delay(br, BR_MIN_FORWARD_DELAY); else if (br->bridge_forward_delay > BR_MAX_FORWARD_DELAY) __br_set_forward_delay(br, BR_MAX_FORWARD_DELAY); ---------------------> can you enable debug print for this to see what ---------------------> you end up using? if (!err) { br->stp_enabled = BR_USER_STP; br_debug(br, "userspace STP started\n"); } else { br->stp_enabled = BR_KERNEL_STP; br_debug(br, "using kernel STP\n"); /* To start timers on any ports left in blocking */ if (br->dev->flags & IFF_UP) mod_timer(&br->hello_timer, jiffies + br->hello_time); br_port_state_selection(br); } -----------------> spin_unlock_bh(&br->lock); }