From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: [PATCH-block v3 1/2] bdi, blk-cgroup: Fix potential UAF of blkcg Date: Tue, 13 Dec 2022 13:44:45 -0500 Message-ID: <20221213184446.50181-2-longman@redhat.com> References: <20221213184446.50181-1-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=1670957103; 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=XKtEb7DX5sCj2p62DhFAWIKVGv8SYAUBUDgGPKa8O/0=; b=Q822aMYKwgls0VAuvvolUQeg/XGipJ3aWV0MZNsRmg6x3024yiDgP+uyOtZc1YwP1ec8fC iRNDixTQaVbuPv6/noR/JLKX7hObjMVaweS0f4a5dvZy7SBLPUHJbk2tp0zAdLGpoQu9Qo D0qPLESQvrKMfbZt98HQ5Uwi/WZsPnk= In-Reply-To: <20221213184446.50181-1-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 ZyA8bG9uZ21hbkByZWRoYXQuY29tPgotLS0KIGJsb2NrL2Jsay1jZ3JvdXAuYyB8IDcgKysrKysr KwogbW0vYmFja2luZy1kZXYuYyAgIHwgOCArKysrKystLQogMiBmaWxlcyBjaGFuZ2VkLCAxMyBp bnNlcnRpb25zKCspLCAyIGRlbGV0aW9ucygtKQoKZGlmZiAtLWdpdCBhL2Jsb2NrL2Jsay1jZ3Jv dXAuYyBiL2Jsb2NrL2Jsay1jZ3JvdXAuYwppbmRleCAxYmI5MzlkM2I3OTMuLmNhMjgzMDZhYTFi MSAxMDA2NDQKLS0tIGEvYmxvY2svYmxrLWNncm91cC5jCisrKyBiL2Jsb2NrL2Jsay1jZ3JvdXAu YwpAQCAtMTA4NCw2ICsxMDg0LDEzIEBAIHN0cnVjdCBsaXN0X2hlYWQgKmJsa2NnX2dldF9jZ3di X2xpc3Qoc3RydWN0IGNncm91cF9zdWJzeXNfc3RhdGUgKmNzcykKICAqLwogc3RhdGljIHZvaWQg YmxrY2dfZGVzdHJveV9ibGtncyhzdHJ1Y3QgYmxrY2cgKmJsa2NnKQogeworCS8qCisJICogYmxr Y2dfZGVzdHJveV9ibGtncygpIHNob3VsZG4ndCBiZSBjYWxsZWQgd2l0aCBhbGwgdGhlIGJsa2Nn CisJICogcmVmZXJlbmNlcyBnb25lLgorCSAqLworCWlmIChXQVJOX09OX09OQ0UocGVyY3B1X3Jl Zl9pc196ZXJvKCZibGtjZy0+Y3NzLnJlZmNudCkpKQorCQlyZXR1cm47CisKIAltaWdodF9zbGVl cCgpOwogCiAJc3Bpbl9sb2NrX2lycSgmYmxrY2ctPmxvY2spOwpkaWZmIC0tZ2l0IGEvbW0vYmFj a2luZy1kZXYuYyBiL21tL2JhY2tpbmctZGV2LmMKaW5kZXggYzMwNDE5YTVlMTE5Li4zNmY3NWIw NzIzMjUgMTAwNjQ0Ci0tLSBhL21tL2JhY2tpbmctZGV2LmMKKysrIGIvbW0vYmFja2luZy1kZXYu YwpAQCAtMzkwLDExICszOTAsMTUgQEAgc3RhdGljIHZvaWQgY2d3Yl9yZWxlYXNlX3dvcmtmbihz dHJ1Y3Qgd29ya19zdHJ1Y3QgKndvcmspCiAJd2Jfc2h1dGRvd24od2IpOwogCiAJY3NzX3B1dCh3 Yi0+bWVtY2dfY3NzKTsKLQljc3NfcHV0KHdiLT5ibGtjZ19jc3MpOwogCW11dGV4X3VubG9jaygm d2ItPmJkaS0+Y2d3Yl9yZWxlYXNlX211dGV4KTsKIAotCS8qIHRyaWdnZXJzIGJsa2cgZGVzdHJ1 Y3Rpb24gaWYgbm8gb25saW5lIHVzZXJzIGxlZnQgKi8KKwkvKgorCSAqIFRyaWdnZXJzIGJsa2cg ZGVzdHJ1Y3Rpb24gaWYgbm8gb25saW5lIHVzZXJzIGxlZnQKKwkgKiBUaGUgZmluYWwgYmxrY2cg Y3NzX3B1dCgpIGhhcyB0byBiZSBkb25lIGFmdGVyIGJsa2NnX3VucGluX29ubGluZSgpCisJICog dG8gYXZvaWQgdXNlLWFmdGVyLWZyZWUuCisJICovCiAJYmxrY2dfdW5waW5fb25saW5lKHdiLT5i bGtjZ19jc3MpOworCWNzc19wdXQod2ItPmJsa2NnX2Nzcyk7CiAKIAlmcHJvcF9sb2NhbF9kZXN0 cm95X3BlcmNwdSgmd2ItPm1lbWNnX2NvbXBsZXRpb25zKTsKIAotLSAKMi4zMS4xCgo= 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 27C36C4332F for ; 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Tue, 13 Dec 2022 13:44:59 -0500 X-MC-Unique: QAxSZuDjMui-EVsI4VfzIg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9962D3C10147; Tue, 13 Dec 2022 18:44:58 +0000 (UTC) Received: from llong.com (unknown [10.22.32.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id F370BC15BA0; Tue, 13 Dec 2022 18:44:57 +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 v3 1/2] bdi, blk-cgroup: Fix potential UAF of blkcg Date: Tue, 13 Dec 2022 13:44:45 -0500 Message-Id: <20221213184446.50181-2-longman@redhat.com> In-Reply-To: <20221213184446.50181-1-longman@redhat.com> References: <20221213184446.50181-1-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 10.11.54.8 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 | 7 +++++++ mm/backing-dev.c | 8 ++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 1bb939d3b793..ca28306aa1b1 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(percpu_ref_is_zero(&blkcg->css.refcnt))) + return; + might_sleep(); spin_lock_irq(&blkcg->lock); 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