From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: [PATCH-block 1/3] bdi, blk-cgroup: Fix potential UAF of blkcg Date: Thu, 8 Dec 2022 17:01:39 -0500 Message-ID: <20221208220141.2625775-2-longman@redhat.com> References: <20221208220141.2625775-1-longman@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: base64 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670536915; 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: in-reply-to:in-reply-to:references:references; bh=+MsWk87quHbEwHCR1sVYteGgGZjHdGBkMWIDf/Jp0nk=; b=gIMUqKc4BHkBF0wmgoZGsA09GL51xoSjKy8yXjU/xuX7WUh1L17YFzHdCfoHBLhUFkFIO1 1hdqr8a5jJF+LJws06N4Rf/6/wh8ez5z2iaCmcB0PWIVtvURE8R2mtSz1O+aKoVwlRx018 SYvrdGmI8FrXkiRaAQ2DLdG33aS372U= In-Reply-To: <20221208220141.2625775-1-longman@redhat.com> List-ID: Content-Type: text/plain; charset="macroman" To: Jens Axboe , Tejun Heo , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?q?Michal=20Koutn=C3=BD?= , "Dennis Zhou (Facebook)" , Waiman Long , Yi Zhang Q29tbWl0IDU5YjU3NzE3ZmZmOCAoImJsa2NnOiBkZWxheSBibGtnIGRlc3RydWN0aW9uIHVudGls IGFmdGVyCndyaXRlYmFjayBoYXMgZmluaXNoZWQiKSBkZWxheWVkIGNhbGwgdG8gYmxrY2dfZGVz dHJveV9ibGtncygpIHRvCmNnd2JfcmVsZWFzZV93b3JrZm4oKS4gSG93ZXZlciwgaXQgaXMgZG9u ZSBhZnRlciBhIGNzc19wdXQoKSBvZiBibGtjZwp3aGljaCBtYXkgYmUgdGhlIGZpbmFsIHB1dCB0 aGF0IGNhdXNlcyB0aGUgYmxrY2cgdG8gYmUgZnJlZWQgYXMgUkNVCnJlYWQgbG9jayBpc24ndCBo ZWxkLgoKQW5vdGhlciBwbGFjZSB3aGVyZSBibGtjZ19kZXN0cm95X2Jsa2dzKCkgY2FuIGJlIGNh bGxlZCBpbmRpcmVjdGx5IHZpYQpibGtjZ191bnBpbl9vbmxpbmUoKSBpcyBmcm9tIHRoZSBvZmZs aW5lX2NzcygpIGZ1bmN0aW9uIGNhbGxlZCBmcm9tCmNzc19raWxsZWRfd29ya19mbigpLiBPdmVy IHRoZXJlLCB0aGUgcG90ZW50aWFsbHkgZmluYWwgY3NzX3B1dCgpIGNhbGwKaXMgaXNzdWVkIGFm dGVyIG9mZmxpbmVfY3NzKCkuCgpCeSBhZGRpbmcgYSBjc3NfdHJ5Z2V0KCkgaW50byBibGtjZ19k ZXN0cm95X2Jsa2dzKCkgYW5kIHdhcm5pbmcgaXRzCmZhaWx1cmUsIHRoZSBmb2xsb3dpbmcgc3Rh Y2sgdHJhY2Ugd2FzIHByb2R1Y2VkIGluIGEgdGVzdCBzeXN0ZW0gb24KYm9vdHVwLgoKWyAgIDM0 LjI1NDI0MF0gUklQOiAwMDEwOmJsa2NnX2Rlc3Ryb3lfYmxrZ3MrMHgxNmEvMHgxYTAKICAgICAg OgpbICAgMzQuMzM5OTQzXSBDYWxsIFRyYWNlOgpbICAgMzQuMzQ0NTEwXSAgYmxrY2dfdW5waW5f b25saW5lKzB4MzgvMHg2MApbICAgMzQuMzQ4NTIzXSAgY2d3Yl9yZWxlYXNlX3dvcmtmbisweDZh LzB4MjAwClsgICAzNC4zNTI3MDhdICBwcm9jZXNzX29uZV93b3JrKzB4MWU1LzB4M2IwClsgICAz NC4zNjA3NThdICB3b3JrZXJfdGhyZWFkKzB4NTAvMHgzYTAKWyAgIDM0LjM2ODQ0N10gIGt0aHJl YWQrMHhkOS8weDEwMApbICAgMzQuMzc2Mzg2XSAgcmV0X2Zyb21fZm9yaysweDIyLzB4MzAKClRo aXMgY29uZmlybXMgdGhhdCBhIHBvdGVudGlhbCBVQUYgc2l0dWF0aW9uIGNhbiByZWFsbHkgaGFw cGVuIGluCmNnd2JfcmVsZWFzZV93b3JrZm4oKS4KCkZpeCB0aGF0IGJ5IGRlbGF5aW5nIHRoZSBj c3NfcHV0KCkgdW50aWwgYWZ0ZXIgdGhlIGJsa2NnX3VucGluX29ubGluZSgpCmNhbGwuIEFsc28g dXNlIGNzc190cnlnZXQoKSBpbiBibGtjZ19kZXN0cm95X2Jsa2dzKCkgYW5kIGlzc3VlIGEgd2Fy bmluZwppZiBjc3NfdHJ5Z2V0KCkgZmFpbHMuCgpUaGUgcmVwcm9kdWNpbmcgc3lzdGVtIGNhbiBu byBsb25nZXIgcHJvZHVjZSBhIHdhcm5pbmcgd2l0aCB0aGlzIHBhdGNoLgpBbGwgdGhlIHJ1bm5h YmxlIGJsb2NrLzAqIHRlc3RzIGluY2x1ZGluZyBibG9jay8wMjcgd2VyZSBydW4gc3VjY2Vzc2Z1 bGx5CndpdGhvdXQgZmFpbHVyZS4KCkZpeGVzOiA1OWI1NzcxN2ZmZjggKCJibGtjZzogZGVsYXkg YmxrZyBkZXN0cnVjdGlvbiB1bnRpbCBhZnRlciB3cml0ZWJhY2sgaGFzIGZpbmlzaGVkIikKU3Vn Z2VzdGVkLWJ5OiBNaWNoYWwgS291dG7DvSA8bWtvdXRueUBzdXNlLmNvbT4KUmVwb3J0ZWQtYnk6 IFlpIFpoYW5nIDx5aS56aGFuZ0ByZWRoYXQuY29tPgpTaWduZWQtb2ZmLWJ5OiBXYWltYW4gTG9u ZyA8bG9uZ21hbkByZWRoYXQuY29tPgotLS0KIGJsb2NrL2Jsay1jZ3JvdXAuYyB8IDggKysrKysr KysKIG1tL2JhY2tpbmctZGV2LmMgICB8IDggKysrKysrLS0KIDIgZmlsZXMgY2hhbmdlZCwgMTQg aW5zZXJ0aW9ucygrKSwgMiBkZWxldGlvbnMoLSkKCmRpZmYgLS1naXQgYS9ibG9jay9ibGstY2dy b3VwLmMgYi9ibG9jay9ibGstY2dyb3VwLmMKaW5kZXggMWJiOTM5ZDNiNzkzLi4yMWNjODgzNDlm MjEgMTAwNjQ0Ci0tLSBhL2Jsb2NrL2Jsay1jZ3JvdXAuYworKysgYi9ibG9jay9ibGstY2dyb3Vw LmMKQEAgLTEwODQsNiArMTA4NCwxMyBAQCBzdHJ1Y3QgbGlzdF9oZWFkICpibGtjZ19nZXRfY2d3 Yl9saXN0KHN0cnVjdCBjZ3JvdXBfc3Vic3lzX3N0YXRlICpjc3MpCiAgKi8KIHN0YXRpYyB2b2lk IGJsa2NnX2Rlc3Ryb3lfYmxrZ3Moc3RydWN0IGJsa2NnICpibGtjZykKIHsKKwkvKgorCSAqIGJs a2NnX2Rlc3Ryb3lfYmxrZ3MoKSBzaG91bGRuJ3QgYmUgY2FsbGVkIHdpdGggYWxsIHRoZSBibGtj ZworCSAqIHJlZmVyZW5jZXMgZ29uZS4KKwkgKi8KKwlpZiAoV0FSTl9PTl9PTkNFKCFjc3NfdHJ5 Z2V0KCZibGtjZy0+Y3NzKSkpCisJCXJldHVybjsKKwogCW1pZ2h0X3NsZWVwKCk7CiAKIAlzcGlu X2xvY2tfaXJxKCZibGtjZy0+bG9jayk7CkBAIC0xMTEwLDYgKzExMTcsNyBAQCBzdGF0aWMgdm9p ZCBibGtjZ19kZXN0cm95X2Jsa2dzKHN0cnVjdCBibGtjZyAqYmxrY2cpCiAJfQogCiAJc3Bpbl91 bmxvY2tfaXJxKCZibGtjZy0+bG9jayk7CisJY3NzX3B1dCgmYmxrY2ctPmNzcyk7CiB9CiAKIC8q KgpkaWZmIC0tZ2l0IGEvbW0vYmFja2luZy1kZXYuYyBiL21tL2JhY2tpbmctZGV2LmMKaW5kZXgg YzMwNDE5YTVlMTE5Li4zNmY3NWIwNzIzMjUgMTAwNjQ0Ci0tLSBhL21tL2JhY2tpbmctZGV2LmMK KysrIGIvbW0vYmFja2luZy1kZXYuYwpAQCAtMzkwLDExICszOTAsMTUgQEAgc3RhdGljIHZvaWQg Y2d3Yl9yZWxlYXNlX3dvcmtmbihzdHJ1Y3Qgd29ya19zdHJ1Y3QgKndvcmspCiAJd2Jfc2h1dGRv d24od2IpOwogCiAJY3NzX3B1dCh3Yi0+bWVtY2dfY3NzKTsKLQljc3NfcHV0KHdiLT5ibGtjZ19j c3MpOwogCW11dGV4X3VubG9jaygmd2ItPmJkaS0+Y2d3Yl9yZWxlYXNlX211dGV4KTsKIAotCS8q IHRyaWdnZXJzIGJsa2cgZGVzdHJ1Y3Rpb24gaWYgbm8gb25saW5lIHVzZXJzIGxlZnQgKi8KKwkv KgorCSAqIFRyaWdnZXJzIGJsa2cgZGVzdHJ1Y3Rpb24gaWYgbm8gb25saW5lIHVzZXJzIGxlZnQK KwkgKiBUaGUgZmluYWwgYmxrY2cgY3NzX3B1dCgpIGhhcyB0byBiZSBkb25lIGFmdGVyIGJsa2Nn X3VucGluX29ubGluZSgpCisJICogdG8gYXZvaWQgdXNlLWFmdGVyLWZyZWUuCisJICovCiAJYmxr Y2dfdW5waW5fb25saW5lKHdiLT5ibGtjZ19jc3MpOworCWNzc19wdXQod2ItPmJsa2NnX2Nzcyk7 CiAKIAlmcHJvcF9sb2NhbF9kZXN0cm95X3BlcmNwdSgmd2ItPm1lbWNnX2NvbXBsZXRpb25zKTsK IAotLSAKMi4zMS4xCgo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31975C001B2 for ; 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Thu, 08 Dec 2022 17:01:52 -0500 X-MC-Unique: PtZEtElbO9W4Ys0KShUpYA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 60E4785A588; Thu, 8 Dec 2022 22:01:51 +0000 (UTC) Received: from llong.com (dhcp-17-153.bos.redhat.com [10.18.17.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id F079E17582; Thu, 8 Dec 2022 22:01:50 +0000 (UTC) From: Waiman Long To: Jens Axboe , Tejun Heo , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?q?Michal=20Koutn=C3=BD?= , "Dennis Zhou (Facebook)" , Waiman Long , Yi Zhang Subject: [PATCH-block 1/3] bdi, blk-cgroup: Fix potential UAF of blkcg Date: Thu, 8 Dec 2022 17:01:39 -0500 Message-Id: <20221208220141.2625775-2-longman@redhat.com> In-Reply-To: <20221208220141.2625775-1-longman@redhat.com> References: <20221208220141.2625775-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Commit 59b57717fff8 ("blkcg: delay blkg destruction until after writeback has finished") delayed call to blkcg_destroy_blkgs() to cgwb_release_workfn(). However, it is done after a css_put() of blkcg which may be the final put that causes the blkcg to be freed as RCU read lock isn't held. Another place where blkcg_destroy_blkgs() can be called indirectly via blkcg_unpin_online() is from the offline_css() function called from css_killed_work_fn(). Over there, the potentially final css_put() call is issued after offline_css(). By adding a css_tryget() into blkcg_destroy_blkgs() and warning its failure, the following stack trace was produced in a test system on bootup. [ 34.254240] RIP: 0010:blkcg_destroy_blkgs+0x16a/0x1a0 : [ 34.339943] Call Trace: [ 34.344510] blkcg_unpin_online+0x38/0x60 [ 34.348523] cgwb_release_workfn+0x6a/0x200 [ 34.352708] process_one_work+0x1e5/0x3b0 [ 34.360758] worker_thread+0x50/0x3a0 [ 34.368447] kthread+0xd9/0x100 [ 34.376386] ret_from_fork+0x22/0x30 This confirms that a potential UAF situation can really happen in cgwb_release_workfn(). Fix that by delaying the css_put() until after the blkcg_unpin_online() call. Also use css_tryget() in blkcg_destroy_blkgs() and issue a warning if css_tryget() fails. The reproducing system can no longer produce a warning with this patch. All the runnable block/0* tests including block/027 were run successfully without failure. Fixes: 59b57717fff8 ("blkcg: delay blkg destruction until after writeback has finished") Suggested-by: Michal Koutný Reported-by: Yi Zhang Signed-off-by: Waiman Long --- block/blk-cgroup.c | 8 ++++++++ mm/backing-dev.c | 8 ++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 1bb939d3b793..21cc88349f21 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1084,6 +1084,13 @@ struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css) */ static void blkcg_destroy_blkgs(struct blkcg *blkcg) { + /* + * blkcg_destroy_blkgs() shouldn't be called with all the blkcg + * references gone. + */ + if (WARN_ON_ONCE(!css_tryget(&blkcg->css))) + return; + might_sleep(); spin_lock_irq(&blkcg->lock); @@ -1110,6 +1117,7 @@ static void blkcg_destroy_blkgs(struct blkcg *blkcg) } spin_unlock_irq(&blkcg->lock); + css_put(&blkcg->css); } /** diff --git a/mm/backing-dev.c b/mm/backing-dev.c index c30419a5e119..36f75b072325 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -390,11 +390,15 @@ static void cgwb_release_workfn(struct work_struct *work) wb_shutdown(wb); css_put(wb->memcg_css); - css_put(wb->blkcg_css); mutex_unlock(&wb->bdi->cgwb_release_mutex); - /* triggers blkg destruction if no online users left */ + /* + * Triggers blkg destruction if no online users left + * The final blkcg css_put() has to be done after blkcg_unpin_online() + * to avoid use-after-free. + */ blkcg_unpin_online(wb->blkcg_css); + css_put(wb->blkcg_css); fprop_local_destroy_percpu(&wb->memcg_completions); -- 2.31.1