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Wed, 21 Apr 2021 11:25:32 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-99-fI8GWUH2NUO9W6kUTUAkJQ-1; Wed, 21 Apr 2021 11:24:42 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3A79710A23C1; Wed, 21 Apr 2021 15:22:52 +0000 (UTC) Received: from worklaptop.home (ovpn-117-254.rdu2.redhat.com [10.10.117.254]) by smtp.corp.redhat.com (Postfix) with ESMTP id BBBC35C1B4; Wed, 21 Apr 2021 15:22:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619018728; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=CCtmOtwws9SINVeLkgek76f/V4rXU+1c62jCYog0mqU=; b=Y7ZOQI8n89J9o4FzZYze4zgz9SumnTeBJNP1WtttUYYslKHgab/I6ijE9zYppT19tBUsvy yyM9sLSXC4rvIAsYikYdi1sa53K4ZO1PpQgbt9mt+qWkm9cyjrsG4w/c38O9rmA60yns6o jIRinpBA46PoUJ+Bk/42XqnZAUCGDow= X-MC-Unique: fI8GWUH2NUO9W6kUTUAkJQ-1 From: Cole Robinson To: qemu-devel@nongnu.org Subject: [PATCH-for-6.0] net: tap: fix crash on hotplug Date: Wed, 21 Apr 2021 11:22:45 -0400 Message-Id: <3f6be9c84782a0943ea21a8a6f8a5d055b65f2d5.1619018363.git.crobinso@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=crobinso@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=216.205.24.124; envelope-from=crobinso@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , jasowang@redhat.com, Cole Robinson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" Attempting to hotplug a tap nic with libvirt will crash qemu: $ sudo virsh attach-interface f32 network default error: Failed to attach interface error: Unable to read from monitor: Connection reset by peer 0x000055875b7f3a99 in tap_send (opaque=3D0x55875e39eae0) at ../net/tap.c:206 206 if (!s->nc.peer->do_not_pad) { gdb$ bt s->nc.peer may not be set at this point. This seems to be an expected case, as qemu_send_packet_* explicitly checks for NULL s->nc.peer later. Fix it by checking for s->nc.peer here too. Padding is applied if s->nc.peer is not set. https://bugzilla.redhat.com/show_bug.cgi?id=3D1949786 Fixes: 969e50b61a2 Signed-off-by: Cole Robinson --- * Or should we skip padding if nc.peer is unset? I didn't dig into it * tap-win3.c and slirp.c may need a similar fix, but the slirp case didn't crash in a simple test. net/tap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/tap.c b/net/tap.c index dd42ac6134..937559dbb8 100644 --- a/net/tap.c +++ b/net/tap.c @@ -203,7 +203,7 @@ static void tap_send(void *opaque) size -=3D s->host_vnet_hdr_len; } =20 - if (!s->nc.peer->do_not_pad) { + if (!s->nc.peer || !s->nc.peer->do_not_pad) { if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) { buf =3D min_pkt; size =3D min_pktsz; --=20 2.31.1