From nobody Tue Feb 10 04:15:12 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1494842603968906.4578489917236; Mon, 15 May 2017 03:03:23 -0700 (PDT) Received: from localhost ([::1]:35752 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dACqY-0001yV-Ix for importer@patchew.org; Mon, 15 May 2017 06:03:22 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49563) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dACoZ-0000ax-Eq for qemu-devel@nongnu.org; Mon, 15 May 2017 06:01:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dACoU-0005tH-K1 for qemu-devel@nongnu.org; Mon, 15 May 2017 06:01:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38422) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dACoN-0005pM-Vh; Mon, 15 May 2017 06:01:08 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C9C87CA1C4; Mon, 15 May 2017 10:01:06 +0000 (UTC) Received: from donizetti.redhat.com (ovpn-116-102.ams2.redhat.com [10.36.116.102]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v4FA10Ak004293; Mon, 15 May 2017 06:01:05 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C9C87CA1C4 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=pbonzini@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com C9C87CA1C4 From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Mon, 15 May 2017 12:00:55 +0200 Message-Id: <20170515100059.15795-4-pbonzini@redhat.com> In-Reply-To: <20170515100059.15795-1-pbonzini@redhat.com> References: <20170515100059.15795-1-pbonzini@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 15 May 2017 10:01:07 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v3 3/7] curl: avoid recursive locking of BDRVCURLState mutex X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jcody@redhat.com, rjones@redhat.com, qemu-block@nongnu.org, qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The curl driver has a ugly hack where, if it cannot find an empty CURLState, it just uses aio_poll to wait for one to be empty. This is probably buggy when used together with dataplane, and the simplest way to fix it is to use coroutines instead. A more immediate effect of the bug however is that it can cause a recursive call to curl_readv_bh_cb and recursively taking the BDRVCURLState mutex. This causes a deadlock. The fix is to unlock the mutex around aio_poll, but for cleanliness we should also take the mutex around all calls to curl_init_state, even if reaching the unlock/lock pair is impossible. The same is true for curl_clean_state. Reported-by: Kun Wei Tested-by: Richard W.M. Jones Cc: qemu-stable@nongnu.org Cc: Jeff Cody Signed-off-by: Paolo Bonzini --- v2->v3: add missing qemu_mutex_destroy on failure case block/curl.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/block/curl.c b/block/curl.c index 924c2a2088..5e6ddf3a34 100644 --- a/block/curl.c +++ b/block/curl.c @@ -281,6 +281,7 @@ read_end: return size * nmemb; } =20 +/* Called with s->mutex held. */ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len, CURLAIOCB *acb) { @@ -453,6 +454,7 @@ static void curl_multi_timeout_do(void *arg) #endif } =20 +/* Called with s->mutex held. */ static CURLState *curl_init_state(BlockDriverState *bs, BDRVCURLState *s) { CURLState *state =3D NULL; @@ -471,7 +473,9 @@ static CURLState *curl_init_state(BlockDriverState *bs,= BDRVCURLState *s) break; } if (!state) { + qemu_mutex_unlock(&s->mutex); aio_poll(bdrv_get_aio_context(bs), true); + qemu_mutex_lock(&s->mutex); } } while(!state); =20 @@ -534,6 +538,7 @@ static CURLState *curl_init_state(BlockDriverState *bs,= BDRVCURLState *s) return state; } =20 +/* Called with s->mutex held. */ static void curl_clean_state(CURLState *s) { int j; @@ -565,6 +570,7 @@ static void curl_detach_aio_context(BlockDriverState *b= s) BDRVCURLState *s =3D bs->opaque; int i; =20 + qemu_mutex_lock(&s->mutex); for (i =3D 0; i < CURL_NUM_STATES; i++) { if (s->states[i].in_use) { curl_clean_state(&s->states[i]); @@ -580,6 +586,7 @@ static void curl_detach_aio_context(BlockDriverState *b= s) curl_multi_cleanup(s->multi); s->multi =3D NULL; } + qemu_mutex_unlock(&s->mutex); =20 timer_del(&s->timer); } @@ -677,6 +684,7 @@ static int curl_open(BlockDriverState *bs, QDict *optio= ns, int flags, return -EROFS; } =20 + qemu_mutex_init(&s->mutex); opts =3D qemu_opts_create(&runtime_opts, NULL, 0, &error_abort); qemu_opts_absorb_qdict(opts, options, &local_err); if (local_err) { @@ -747,7 +755,9 @@ static int curl_open(BlockDriverState *bs, QDict *optio= ns, int flags, DPRINTF("CURL: Opening %s\n", file); s->aio_context =3D bdrv_get_aio_context(bs); s->url =3D g_strdup(file); + qemu_mutex_lock(&s->mutex); state =3D curl_init_state(bs, s); + qemu_mutex_unlock(&s->mutex); if (!state) goto out_noclean; =20 @@ -791,11 +801,12 @@ static int curl_open(BlockDriverState *bs, QDict *opt= ions, int flags, } DPRINTF("CURL: Size =3D %zd\n", s->len); =20 + qemu_mutex_lock(&s->mutex); curl_clean_state(state); + qemu_mutex_unlock(&s->mutex); curl_easy_cleanup(state->curl); state->curl =3D NULL; =20 - qemu_mutex_init(&s->mutex); curl_attach_aio_context(bs, bdrv_get_aio_context(bs)); =20 qemu_opts_del(opts); @@ -806,6 +817,7 @@ out: curl_easy_cleanup(state->curl); state->curl =3D NULL; out_noclean: + qemu_mutex_destroy(&s->mutex); g_free(s->cookie); g_free(s->url); qemu_opts_del(opts); --=20 2.12.2