From nobody Mon Feb 9 14:38:13 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 1494950434714161.33951691030882; Tue, 16 May 2017 09:00:34 -0700 (PDT) Received: from localhost ([::1]:42928 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dAetl-00082r-7j for importer@patchew.org; Tue, 16 May 2017 12:00:33 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46796) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dAeoC-0003UX-Tg for qemu-devel@nongnu.org; Tue, 16 May 2017 11:54:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dAeoB-0001dt-Tl for qemu-devel@nongnu.org; Tue, 16 May 2017 11:54:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54506) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dAeo7-0001a0-Va; Tue, 16 May 2017 11:54:44 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8F57BC04B920; Tue, 16 May 2017 15:54:32 +0000 (UTC) Received: from localhost (ovpn-116-10.phx2.redhat.com [10.3.116.10]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 44570A92A8; Tue, 16 May 2017 15:54:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 8F57BC04B920 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jcody@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 8F57BC04B920 From: Jeff Cody To: qemu-block@nongnu.org Date: Tue, 16 May 2017 11:54:16 -0400 Message-Id: <20170516155420.10106-5-jcody@redhat.com> In-Reply-To: <20170516155420.10106-1-jcody@redhat.com> References: <20170516155420.10106-1-jcody@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 16 May 2017 15:54:42 +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] [PULL 4/8] 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: peter.maydell@linaro.org, jcody@redhat.com, qemu-stable@nongnu.org, qemu-devel@nongnu.org, Paolo Bonzini 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" From: Paolo Bonzini 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 Reviewed-by: Max Reitz Reviewed-by: Jeff Cody Signed-off-by: Paolo Bonzini Message-id: 20170515100059.15795-4-pbonzini@redhat.com Cc: qemu-stable@nongnu.org Cc: Jeff Cody Signed-off-by: Paolo Bonzini Signed-off-by: Jeff Cody --- block/curl.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/block/curl.c b/block/curl.c index 18b82bc..c160810 100644 --- a/block/curl.c +++ b/block/curl.c @@ -282,6 +282,7 @@ 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) { @@ -454,6 +455,7 @@ 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; @@ -472,7 +474,9 @@ 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 @@ -535,6 +539,7 @@ 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; @@ -566,6 +571,7 @@ 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]); @@ -581,6 +587,7 @@ 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); } @@ -684,6 +691,7 @@ 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) { @@ -769,7 +777,9 @@ 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 @@ -813,11 +823,12 @@ 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); @@ -828,6 +839,7 @@ 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 2.9.3